3D Realms - Crystal Caves

The official Crystal Caves page, from its creators. There is a link to purchasing the game.
http://www.3drealms.com/caves/

GameFAQs: Crystal Caves

Reviewed by KBroccoli, 6.5/10. "A more thorough gaming experience than the Commander Keen saga, it's a perfect little game for the fans of that kind of PC gaming or those after a touch of nostalgia."
http://www.gamefaqs.com/computer/doswin/review/R23805.html

Crystal Caves

Provides downloads, screenshots, cheats, and links.
http://www.geocities.com/crystalcaveswebsite/