The existence of ancient civilizations is a recurring element in the Final Fantasy series. They have often faded from current zeitgeist, and are the origin of artifacts and ruins, or have left behind written works the modern civilization struggles to interpret. Ancient civilizations tend to have been more powerful than the current civilizations, and their advanced technology or magic has been lost to the rifts of time, and is sometimes being rediscovered by modern peoples.
The treasures and pieces of technology left behind by ancient civilizations are often beyond the modern peoples' understanding, and the ruins associated with these civilizations are full of complicated traps and arcane knowledge. Sometimes, the ancient people who populated these civilizations are viewed as different race altogether, usually meaning they employed a type of magic that has since fallen out of use.
Ancient civilizations being more advanced than the modern ones is a common RPG trope. It allows developers to design dungeons, and particularly bonus dungeons, with powerful mechanisms whose workings don't need to be explained, and adds to the mystery and discovery of the world. They also enable the use of plot devices, like new types of magic or powerful artifacts or pieces of legendary technology being discovered, airships being a common one in the Final Fantasy series. These discoveries can be made by antagonists who pursue world domination, and by the heroes who need a "trump card" to persist against the overwhelming power of the villains. Story and content wise, ancient civilizations may come to serve as a reminder or example of many things, be it the potential good that civilization can achieve, or the retribution brought onto the decadent and wicked.
The Lufenians are descendants of a race called the Sky People who once lived up in the skies. At present, Lufenians live in the remote town of Lufenia. Four hundred years ago the Sky People were the civilization of the highest order. With their mastery of the Wind element, they created a floating castle in the sky. Some boasted that their civilization even reached beyond the skies. The Sky People had invented many types of technology, and a Lufenian called Cid invented the airship. After the Sky People's civilization fell apart, they passed on a legend that four hundred years later, four light-bearers will save them.
There also used to be an ocean-based civilization that was destroyed by violent storms two hundred years ago, and the shrine that served as the center of the civilization sank.
Long ago the Lunarians lived on a planet between the "Red Planet" (Mars) and the "Great Behemoth" (Jupiter). Their home planet was about to be destroyed, so they fled to the "Blue Planet" (Earth), and discovered humans still in the process of evolution. The Lunarians decided to await the day the humans could understand and live peacefully with them, so a second moon was created in orbit over the planet.
Eight of the sixteen Crystals the Lunarians possessed were taken to Earth, presumably to either speed up the evolution of the humans, or to harmonize the Red Moon with the planet to stabilize its orbit. The Lunarians went to sleep near the moon's core. One of the Lunarians, Kluya, built an airship known as the Lunar Whale to travel to Earth where he taught advanced technology, such as airship building and the Devil's Road, and the secret of magic, to the locals.
The ancient Ronka Ruins were built by the Ronka civilization who worshiped the Earth Crystal, the power-source of this flying city. The floating city was built because people believed the sun had the power to cure disease and wanted to live closer to it. The anti-gravity technology used to lift Ronka was the same as used in creating airships. The Catapult is an ancient underwater hangar of the Ronka civilization and holds within chambers a library and a laboratory. The Library of the Ancients is a library filled with books possessed by demons, and in current times is occupied by scholars who try to discern its wonders.
The Magi were the people who partook in the War of the Magi 1,000 years ago. They were the humans who could wield magic, but after the war they were persecuted by non-magic-wielding humans, and went into hiding. The Ultima Weapon was created during the War of the Magi as a magical weapon said to reflect the power of who wields it, but this legendary weapon has since been lost.
Ancient Castle is a thousand-year-old ruin that was buried under a desert. It was was attacked during the War of the Magi, during which the esper Odin engaged an enemy army before an unnamed sorcerer petrified him, and the castle was defeated. The Queen of the Ancient Castle was also petrified in the basement.
The Cetra, also known as the Ancients, are a race of deeply spiritual humans, who are implied to be the origin of the modern humans. According to Sephiroth, regular humans were Cetra who forsook their migratory nature to form permanent settlements millennia ago. The migrations were a Planet-reverent pursuit of the fabled Promised Land conducted by traveling and cultivating life. The Cetra could commune with the Planet, an ability regular humans lost once they gave up their close relationship with it in favor of leisure and convenience. The Cetra could guide the flow of the Planet's spiritual energy, this being the means by which they cultivated life on the Planet's surface. The Cetra served as the Planet's caretakers until their race was nearly reduced to extinction.
Despite said to have been migratory, the Forgotten Capital hidden behind a magical forest is the remains of the Cetra's capital city. Many of the remaining houses still contain furniture and artifacts indicating the area appears just as it did when it was abandoned. The city contains a machine, which allows one to communicate with the Planet. The Temple of the Ancients was built by the Cetra thousands of years ago to house the Black Materia. Its interior is a maze-like cavern of staircases.
Cetra was a civilization that flourished 4000 years ago. Its people emigrated to other continents and founded the Dollet Empire to the west and Esthar to the east. The Centra civilization spanned the southernmost reaches of the world. The Centra built mobile shelters the size of small cities, able to hover and cross gentle terrain, and which plant in the ground. Centra was eventually destroyed by the Lunar Cry, but their ancestors in Esthar became the next advanced civilization in the world.
Dollet Dukedom is the last remnant of the Holy Dollet Empire, which once governed most of the world. Dollet Empire was the first major settlement started by the people who emigrated from Centra. Most of what used to be part of Dollet Empire is currently governed by Galbadia.
The Deep Sea Research Center is an abandoned, half-sunken laboratory formerly used to research draw effects. Known as "Battleship Island", researchers working at this facility were attempting to develop another draw system, gathering different energy and materials for their study. They were in pursuit of a large draw point said to be found somewhere on the planet. It is said their research used Guardian Forces for their experiments. It is unknown for how long the site has been abandoned, but the technology used there seems unfamiliar to the rest of the world.
Terra was a planet like in the cosmos with a highly advanced magical civilization, and at its peak had flourishing cities. Terrans pursued immortality, and when their planet began to decay, they were desperate to preserve their culture and technology via the magical art Fusion. When Terra's crystal grew old and weak, the Terrans would seek out young planets whose cores had not yet grown and assimilate them. The last Fusion Terra attempted was a disastrous failure, and the planet of Terra is left empty and decaying with some of its landmarks becoming mysterious landmarks, such as Oeilvert and Ipsen's Castle.
Two other extinct civilizations include the summoners and the mole people. Hundreds of years ago the summoners lived on the Mist Continent with the other peoples, but after a failed summoning experiment, they migrated to Madain Sari, a town they established on the Outer Continent, where they dedicated their lives to researching summon magic. The remnants of the mole people civilization can be found on Mount Gulug.
Zanarkand is a former metropolis at Spira's northernmost edge. It was annihilated by Sin at the end of the Machina War against Bevelle 1,000 years ago. Zanarkand was a city state whose people wished to enhance their lives using a mix of magic imbued within machina. The arts of summoning were prevalent in Zanarkand, referring to one's ability to manifest the dreams of the fayth in corporeal form. After Zanarkand's fall, the knowledge of how to petrify willing souls into fayth was lost, although a number of fayth statues remain in Spira, preserved in the temples of Yevon.
Zanarkand was but one part of the machina civilizations that used to cover Spira, but its ruins are the main thing that is left of that era a thousand years later, although the effects of the Machina War are still visible in modern Spira from the machina ruins in Besaid, the Mi'ihen Highroad, Bikanel Island, and the Calm Lands. Other relics of these civilizations are found in the depths of the ocean. The Al Bhed salvage ancient technology to re-introduce machina to Spira, although it is forbidden by the teachings of Yevon.
According to the Final Fantasy X Ultimania Omega official timeline, machina was invented over 3000 years ago and became powerful enough to surpass magic. According to the Final Fantasy X Scenario Ultimania, the first development in Spira was brought about by the power of magic, but those who could use magic naturally had an advantage, while those who couldn't were discriminated against. Thus the age of the magic civilizations was an age of inequality. When machina was invented it was revolutionary and at first did away with the inequalities and things once thought impossible became an aspect of everyday life. Machina was supposed to be an alternative for those who couldn't use magic, but when it surpassed it new problems arose. Some nations possessed outstanding machina technology, while others didn't, and a new age of inequality began.
Numerous ancient structures remain on Ivalice, including those related to the Occuria, and those related to he Galtean Alliance. The Galtean Alliance was a moment in Ivalice's history when all the great countries were united and during it available technology was significantly different from the present Ivalice. Many references are made to relics of the ancient age that cannot be reproduced in the present time. The architectural style of Galtea is prominent in many locations within Ivalice.
The Sage Knowledge suggests the Occuria used to live on Ivalice among the other races before withdrawing into their own realm. Structures left behind by the Occuria include the abandoned city of Giruvegan and the Pharos tower.
There also exist ruins of unknown ancient civilizations. The ruins on Tchita Uplands for example are said to be studied by researchers from Archades who delve into the mysteries left by "whatever ancient civilization built them."
Yaschas Massif is the site of the ruins of the city-nation of Paddra on Gran Pulse where the Farseers lived before it fell into ruin. Paddra was ruled by Paddra Nsu-Yeul as both its seeress and priestess with Etro as Paddra's patron deity. After civil war destroyed the nation, Yeul renounced her position and left to wander Gran Pulse. Some of the Paddraean architecture resembles the remains of modern skyscrapers. Paddra has long been abandoned, and only monsters and Cie'th wander its streets. The Haerii Archaeopolis is another ruined city on the Archylte Steppe.
It is suggested a lot of Gran Pulse was once populated. The village of Oerba is located at the northernmost edge of the mainland. Its villagers from several clans shared a communal lifestyle, but what remains of the abandoned village is overrun by Cie'th and in the process of being swallowed by an encroaching sea of ashen crystal sand dunes.
Due to the cycle of umbral and astral eras, Hydaelyn has entire layers of ancient civilizations who form a recurring element in the setting. In Eorzea, there are some ruins from ancient civilizations which existed during old eras, the majority being from the Cities of Magic from the Fifth Astral Era, like Mhach, Amdapor, and Nym. Others include Gelmorra, Belah'dia, and Sil'dih. Some instanced dungeons take place in the ruins of those ancient city-states.
The most significant ancient civilization was Allag, which was also the most powerful empire during the Third Astral Era and the most technologically advanced in history. Their actions still persist in the present for being the creators of Dalamud, Azys Lla, the Crystal Tower, and the Ultima Weapon. Their influence and knowledge is so widespread that their old data storage tomestones are collected as a form of currency.
Solheim was a legendary nation that existed two thousand years ago. It ruled over the lands of Eos during an era of peace and prosperity. It was destroyed in the Great War of Old when a mysterious parasite caused the death of millions. Many of the ruins with arcane technology are implied to be linked to Solheim, such as Costlemark Tower and Pitioss Ruins.
The Niflheim Empire's Aldercapt dynasty intends to recreate the Solheim Empire using magitek power, which was developed in Solheim. Final Fantasy XV Scenario Ultimania confirms that Solheim excelled in in machine technology like airships and Magitek Armor. Niflheim thus excavates and explores Solheimian ruins, although lately it has been doing so mainly to capture daemons, at least according to Aranea Highwind.
Ivalice is littered with unexplored lands, ancient ruins and mystical regions. The Forbidden Land Eureka, for example, is a once prosperous capital of the Kashka Dynasty that was destroyed in the Cataclysm. It is now a necrohol, populated by spirits drawn to the shades of its past glory. The ancient cities are used in the game as Wonders, and unlocked as menu entries by sending out party members to errands. The Wonders allude to past Final Fantasy games, but also exist to give the sense of history and depth to Ivalice.
Some of the ancient sites can be visited, but not much is known about the civilizations that had built them. Nelveska Temple is an abandoned temple off the beaten path guarded by Construct 7, suggesting it belonged to a highly advanced civilization, as the knowledge on building robots has been lost.