Here are two arches that I saw in Athens – both of which I saw on a fanatic early morning run through the city. The first is the Arch of Hadrian, constructed in 131AD. It has been standing for over 1800 years.
And the second marks the entrance to part of the ancient Agora. I have not been able to find any information about the actual arch, so if you know anything about it I would love to know. It is not at the main Agora site, but the slightly smaller site where you can find the Tower of the Winds.