Deep beneath the surface of this remote island, at the end of a mile-long rail tunnel, lies this laboratory devoted to discovering the secrets of the slime. Sure, it's green, it's slimy, it smells bad -- but obviously there must be more to it than that! (People can get research grants for anything! Governments doubly so!)
This is the full SlimeLab level -- the "sequel" to Lab17: Storage. There is also a post-disaster variant of this map, Lab17: Quake.
[Warning/apology: I got a little carried away with the scope of the various Lab17 levels, and eventually gave up all hope of keeping the r_speeds respectably low (mostly because I'm spoiled by having good machines to run them on.) Consequently this level is a bit of a hog, and it won't play properly under HL's software display driver. It runs fine on a 2GHz Celeron with OpenGL. You have been warned!]
(11-24-2019) Edit: download link fixed by The Mad Carrot