Dark Kat's Secret Lair, also known as the Underground Lair, is a secret subterranean lair of the sinister Dark Kat and it first appeared in the episode "Night of the Dark Kat" of SWAT Kats: The Radical Squadron. It is a large, underground facility used by Dark Kat as his base of operations.
This lair is found next to an old bridge and under a small warehouse. Inside the warehouse, entry to the main lair can be gained via spiral staircase.
Once down the stairs, one goes across a bridge in what appears to be a sewer like area.
Inside is a large room where Dark Kat sits and monitors his evil plans from. Many monitors hang from the walls, no doubt to various hidden camera views of Megakat City as well as television stations.
The large green chair in which Dark Kat sits on, may be considered throne-like as the devious kat has building plans of ruling his own version Megakat City dubbed "Dark Kat City".