Hi Experts and Masters! This map's the Twisting Tunnels (30x25), and it's great for keeping your players busy fighting burrowing monsters on the way to the actual adventure. Or, instead you can use your alternate version, the Twisting Cave! In this version I removed the East exit and some of the walls near it to make a spacious little area for a boss fight, making this map into a destination in itself! If you want to be really crafty, have your players use the Tunnels map to get to here, maybe even looping them through it a few times until they are certain there's some weird magic afoot.
You other version is a Subterranean recoloring, a nasty greenish-blue cave system where the air is probably not safe to breathe. This one should be good for your more 'wet' locations, deep beneath the surface or adjacent to the city's sewers, places where the air is humid and damp and moss-covered Drow zombies restlessly lurk.