Undercity

The Undercity is a long destroyed city underground city located under New York City. Most of what remains of it are various stone pillar that are over 1,000 feet high, which are large enough to move freely and fight on, especially for ninjas. Because of the pillars' height relative to the ground beneath the deeper darkness beneath them, the Undercity has produced it's own clouds, which occupy every space or crevice between the pillars. (Splinter) has used the Undercity as a battleground in two major battles against his greatest enemies; Victor Falco, who was known Rat King at that time, and Oroku Saki, who was recently mutated into the monstrous Super Shredder.

Trivia

 * All three participant who battled in the Undercity (Splinter, Rat King, and Super Shredder) have fallen into the dark depths between the pillars of the city