The temple of Diana, although there are only a couple of columns left, was one of the 7 ancient wonders of the world.
The library at ephesus was only outmatched by alexandria in it's day. The library was reconstructed using the fallen pillars and is pretty impressive.
There is also a marble walkway that leads to the library that is also very well preserved called the Arcadian way.
Anyway, check out the pictures. There is also the oldest known advertisement that I captured on film. It's pretty interesting.
Also, if you go to Ephesus, try to go early in the morning (I think it opens at 9) or late in the afternoon (closes at 7?). Ephesus was very crowded when I was there, which surprised me since it was October. I can't imagine this place in August.