This should be the gameplay in Civilization, instead of the thing where you train and archaeologist who goes to excavate magically known locations.
Excavation of tunnels and such should just come with a chance of finding artifacts, but it only materializes with the right culture tech unlocked (before some point, buried treasures were just scrapped or sold, not put into museums).
My little village is built on the site of some ancient Japanese village [0] and any construction that involves digging up dirt often also unearths some kind of archaeological find that stops all work for half a year while the archaeologists do their stuff, if they can even be bothered to come.
It’s happened often enough that it’s a wink and a nod that nothing was found. Foremen and anyone ‘in-charge’ will not be on site until any kind of digging is complete.
Excavation of tunnels and such should just come with a chance of finding artifacts, but it only materializes with the right culture tech unlocked (before some point, buried treasures were just scrapped or sold, not put into museums).