Archealogy!

This idea is trivially simple. Do not excavate terrain when placing some dungeons. Let us discover the dungeon by pickaxing it out. Of course we need clues such as partially buried dungeons, treasure buried here maps on NPCs and POI loot drops, etc. Maybe some brushes and fine picks as the general pickaxe might break more detailed and fragile treasures.

Atlas had treasure maps, but while it required a shovel once you got near the target they was incredibly easy to dig up - it is not a terraforming game so you did not actually dig anything. It was more a trigger to get the lootbox to appear.