Azrael's Tear

You go in to raid it of its treasures and, provided it exists, of the Holy Grail. When you enter, the entrance caves in behind you and you are stuck inside. Ah well, nothing to do but continue on to find what you came for... The game utilizes a true 3D engine to display your surroundings, as in Quake. It's heavy on puzzles and light on combat. As you move further on into the ruins you'll encounter ghosts of the inhabitants and hints as to what happened to cause the ruins that surround you now.