Okay, two temples of the "Doric Order", which is a style of architecture, I believe.
The first; the Parthenon (not the Pantheon... I made that mistake a couple of times)... probably Athen's most iconic image.
The Parthenon is the largest structure on the top of the Acropolis (there are a lot of temples on the top of the Acropolis, in various degrees of ruin), and was initially built around 500BC, as a temple to Athena, where it was mainly a treasury. It was later (well, about a millenium later) converted into a Christian temple, and a millenium after than was converted again into a Mosque by the Turks. Unfortunately, before another millenium could pass, it was badly damaged when Venetians invaded Athens because the Turks, very cleverly, used it as an arsenal for gunpowder, and the Venetians decided to blow up the gunpowder, which in turn blew up much of the structure.
It is currently being restored; there was a lot of scaffolding around one end of the Parthenon.
We looked around the Acropolis Museum, which had quite a few of the original sculptures from the parthenon, but we couldn't use cameras in there. Our tour guide also reminded us every few minutes that the British Museum (which is my second favourite museum in the world, after the Science Museum, which is just amazing) has had many of the statues from the Parthenon for about 200 years, and at the moment is refusing to return them to Athens.
The other temple, which is no where near as big, but better preserved, is the temple of Hephaeastus, which is in the Agora. The Agora is just next to the Acropolis, and was a large open meeting place, where people did speeches and there was a large market and... things. That was not a good sentence. Anywho, 2 days ago, the green bit at the bottom of the picture of Athens was the Agora.
The temple itself was on a small hill in the middle-ish of the agora, overlooking things. It's about as old as the Parthenon, and like the Parthenon, eventually became a Christian temple.