Treasure room is a small area(usually inside a building) that only contains treasure without any monsters or NPCs.
May contain traps, chests or loot on ground.
Design guidelines:
1.Restricted access(mazes, locks, levers, hidden passages, tunnels,etc). Players can only get in one way.
2.Not apparent from distance. I.e there isn't a bright signal on minimap.
3.Randomly generated and random location. The treasure room appears randomly in suitable location(changing Room X to Treasure room) and can't be "farmed" repeatedly.
4.Themed with level-specific ornamentation to signify its status: visually the room should not appear as mundane storage space, but as hidden luxury in the level.