From Teenage Mutant Ninja Turtles wiki
New York City
New York City serves as the primary urban battleground for the Teenage Mutant Ninja Turtles, housing their sewer headquarters and the majority of their adversaries.
New York City is the central setting for the adventures of Leonardo, Donatello, Michelangelo, and Raphael. The sprawling metropolis provides a dense network of sewers that the brothers and their mentor, Splinter, utilise as a hidden base of operations. From this subterranean sanctuary, they launch their missions to protect the city from various criminal elements and supernatural threats.
Urban Threats and Allies
The city is frequently plagued by the machinations of Shredder and his Foot Clan, who often operate from hidden strongholds within the urban landscape. Additionally, the presence of advanced technology and extraterrestrial entities like Krang makes the city a focal point for science fiction conflicts. The turtles rely on their close ally April O'Neil, who provides vital information and logistical support from her life on the surface, helping them navigate the complexities of life in the Big Apple while remaining hidden from the public eye.