Woodland Mansions

Looks: the outside is made up of  wood and cobblestone which makes it hard to see in its foresty-biome as only the very top will peek out of the treeline. The inside has many rooms such as a fake end portal room, an obsidian room, a map room and a treasure room. Still inside, you can see in the photo below that the hallways have carpet.

There is plenty of loot but it is defended by axe wielding Vindicators, and Evokers that can summon Vexes which can move through blocks and attack you.