Legend of Grimrock Treasures
In Mount Grimrock, there are seven lost golden Treasures for the hardiest of prisoners to find. Though more or less useless, they do count towards the game's completion statistics. Many of them are very difficult to find, so consult the guide below for instructions. Note that the Treasures do not count towards the Secrets statistic, although some may be found near or within secret areas. Finding all the Treasures unlocks the "Treasure Hunter" Achievement.

Treasure #1 - Golden Chalice

Found On: Level 2: Old Tunnels

Head to the northeast tunnels of Level 2, and you'll eventually find a room with a keyhole on the wall. In this room, there's a hidden switch on the south wall, near the central pillar (A). Press this switch, and then run back to the room just to the west and you'll find a wall has opened. Head inside to claim the Golden Chalice as your own.
Treasure #2 - Golden Deity Figure

Found On: Level 4: Archives (inside Slime Dungeon)

This Treasure can only be accessed via the secret entrance to the Slime Dungeon on Level 3 - please see our walkthrough for details. Once inside, simply search the maze-like room full of Green Slimes, and you'll find the Golden Deity Figure in plain view on the floor at the northeast corner.
Treasure #3 - Crown of Kings

Found On: Level 6: Trapped

Inside the Halls of Fire and its mad-dash, switch-pressing puzzle, you may end up falling down into the lower tunnels on Level 7. While you're there, you might also find a scroll with the word "westmost" on it. This is a clue - you'll need to fall down the westmost pit in the Halls of Fire, behind the central switch column. When you do, you'll end up in the "Golden Grave", facing down a Cave Crab through a gate. Wait about ten seconds, and the gate will open. Defeat the Cave Crab, and claim the Crown of Kings as your own! To leave, exit through the wall that opens up, and make your way to the portal nearby.
Treasure #4 - Ancient Apparatus

Found On: Level 6: Trapped

Inside the secret Fighter's Challenge area (actually on Level 11, but accessed from Level 6), you'll have to do battle with a literal horde of Scavengers. Please see our walkthrough page for more details on how to reach this secret, and how to best the monsters. When you've defeated them, inspect the west wall of the chamber for a hidden switch - press it to reveal the Ancient Apparatus!
Treasure #5 - Golden Dragon

Found On: Level 8: The Vault

Inside the Vault of the Dismantler on Level 8, you'll find more than a legendary sword. The Golden Dragon can be swiped from its resting place by pressing a hidden switch on the southeast wall of the Vault room itself. See our walkthrough page for more details on how to reach the Vault, as it's a big endeavor.
Treasure #6 - Globe of Tetharion

Found On: Level 13: The Cemetery

Down in The Cemetery, you'll find some northern tunnels that can only be opened by a switch on the opposite end of the level. Inside those tunnels, head north until you reach a small dead-end hallway with a Wooden Box inside. Press the hidden switch on the wall and backtrack to the long, south hallway, and follow it to the end (for more detailed instructions, see our Level 13 walkthrough). The Globe of Tetharion will be yours for the taking!
Treasure #7 - Goromorg Miniature

Found On: Level 11: The Tomb

Once you've entered the Tomb of Designers after escaping Level 12, you'll come to a crossroads where you'll need to obtain two Ornate Keys to proceed. Follow the east hall a short ways and look for a runic symbol on the wall. Press it to open up a hidden room containing the last of the game's Treasures, the Goromorg Miniature!