The Turtle Lair is the Sewer home of the Ninja Turtles as well as Splinter. Despite its importance to the characters, it rarely appears with any significance in the video games, usually only as a setting in story cutscenes.
The Lair is first seen in the first home game, where the Turtles return home after defusing the bombs in the Hudson River to find Splinter missing and the home in disarray. Shredder then appears on their TV to taunt them.
The Lair also appears in Turtles in Time's opening cinematic, as the Turtles watch April's TV broadcast that ends up with Krang stealing the Statue of Liberty, and Shredder once again taunting them on-screen. In the Super NES version, the Lair gets a little more "air time", as it is the setting for the game's versus mode, and also makes a short appearance in the game's endings after the credits, as Splinter congratulates his sons on their success and unless played on the hardest difficulty setting, encourages them (i.e. the player) to try a harder difficulty mode.
The Lair's most prominent appearance yet is in 2020's Teenage Mutant Ninja Turtles: Mutant Madness. One of the ways for players to generate more in-game resources is to build and upgrade various rooms in the Lair, including an Ooze Refinery, Scrap Collector, Research Lab and Advanced Lab (for generating Hero Bits), arcade (Season Pass), Portable Portal Generator (Dimension Clash mode), Clan Hall, Dōjō, and Workshop.