New Y'Lyntias is a colony of the ancient Y'Lyntian people in the 2003 TV series.
Description[]
The colony of New Y'Lyntias lay on a rock platform in the middle of a magma lake, which served the city as a natural defensive system. Above the colony hung the indispensable, energizing moon crystal for the life and technology of the Y'Lyntians.

The Crystal Moon of New Y'Lyntias.
The most important building in the city was the High Mage seat, a pointed tower containing a huge vault where the Y'Lyntians had spent their winter hibernation; a "Chamber of Chronicles," in which the history of the Y'lyntian people was recorded; and an armory equipped with lava resistant weapons and armor. Outside the city was another building, which could be reached from the city via a bridge. At the apex of this building, as in the old Y'Lyntias, was a special chamber called the "Star Chamber", from where the High Council was able to pool the energy produced by the Moon Crystal and use it for a series of unexplained tasks.
The city (or at least the magma lake) can be reached via a tunnel secured with heavy bulkheads. The Scots themselves are equipped with locks that react to the energy of the crystals the Y'Lyntians use to operate their technology. To open them, only one crystal fragment needs to be inserted into the notch in the lock, with the polar orientation of each crystal being important to the correct flow of energy to open the door. In order to cross the magma lake, either a cable car that had been set up on one side of the lakeshore or one of the free-flying transport spreaders that the Y'Lyntians used to get around the city was necessary.
History[]

The colony in its heyday.
The colony of New Y'Lyntias was built thousands of years ago in a huge, filled with a magma cavern deep below New York City after the original the kingdom of Y'Lyntias through a series of catastrophic events in which the Y'Lyntians, not innocent, was lost in the sea. Some Y'Lyntians had escaped destruction at the very last moment, along with a large fragment of that crystal whose energy had made old Y'Lyntias the ruling power of its time. Eventually, the refugees reached the East Coast of the United States, and presumably to avoid further reprisal, they built their new abode underground.
The Y'Lyntians soon became accustomed to their new way of life, but some time later, the energy of their life-giving moon crystal began to dry up, forcing most of them to go into a kind of sleep until a cosmic conjunction brought the crystal back with them Energy would feed. Only one of them remained awake to watch over the city: the High Mage, the leader of the New Y'Lyntias High Council.
The Archmage saved the city from intruders and enslaved or destroyed anyone who discovered the city and ventured too deeply into it. Thousands of years later, however, the Turtles and some new friends came to the sunken city to seek refuge. When the High Mage attacked them, the Turtles were forced to defend themselves, and in the course of the ensuing battle, the High Mage himself was put into stasis.

The destruction of New Y'Lyntias.
Months later, however, a conjunction occurred, recharging the moon crystal and waking the people of New Y'Lyntias from their sleep. Most Y'Lyntians, however, had lost none of their old arrogance in their hibernation, and so the High Council began raising the sunken island of Y'Lyntias back to its original location, despite the tectonic and climatic catastrophes that started plaguing the Earth's surface. The Turtles and the moderate Y'Lyntian Versallia, stopped this catastrophic plan by triggering a similar energy feedback as the one that originally destroyed the ancient Y'Lyntias. The star chamber was torn apart and sank together with the crystal moon, which had torn loose from its anchorage on the cave ceiling, and the rest of New Y'Lyntias in the magma lake.