The Vivarium

The Vivarium is the secret underwater lair of The Gibborim, an ancient race of giants who sought to use the help of The Pride in order to destroy the world.  The location is mostly made from stone carvings, with many elaborate decorations that resemble the animal heads of the Gibborim.  There are a variety of different chambers that are all extreme vast in size (presumably due to the gigantic size of the Gibborim) with various pools and giant windows connecting the lair to the ocean.

As the Gibborim were unable to cross over onto Earth without drawing power through soul absorption, it is reasonable to presume that the inter-dimensional boundaries were weaker inside the Vivarium.  It was the scene of the annual Rite of Thunder, in which The Pride would offer a murdered girl's soul for the Gibborim to consume.

The location was destroyed in a confrontation between the Gibborim and The Pride, as they fought to save the lives of their children (the Runaways) from the ancient giants.  As the young team of teenagers escape inside the Leapfrog, the main giant window of the Vivarium explodes.  The explosion is believed to have destroyed the Vivarium and killed all the previous members of The Pride.