The Treasury of Athens

This building (now reconstructed) may have been built to commemorate the victory at the Battle of Marathon in 490 BC.

Or not. Every article I read has a slightly different description or explanation of the buildings and history of Delphi. Unless I really want to delve into the academic literature, I'm not going to know which is correct, and that's in the unlikely event that there's a consensus among the experts.

So I'm just repeating what I was told when I was there, along with what seems to be the most common information online.