Improvements

Archaeological Dig

These improvements turn Antiquity Sites (hidden or otherwise) into either Landmarks or Artifacts. Only Archaeologists can improve Antiquity Sites, and it takes them several turns to get their work done.

It is possible to create one of these dig sites outside of your own territory. You can even create a dig site inside of someone else's territory, though there is a diplomatic penalty associated with doing this. It's still worthwhile in some cases, depending on whether you can get away with being denounced.