Central America - Must see/do in Guatemala City?

The Mrs. and I are going to be in Guatemala City in a couple of weeks. In general, we're frequent and seasoned travels, though this will be our first time in Guatemala.

I've read the typical travel books (LP, Frommers, etc) and have some expectations of the major sites to check out.

I would appreciate a couple of recommendations from FTers that are familiar with GC.

Are there other sites to see or things to do that aren't in your typical travel book?

What are the top restaurants that can't be missed?

We're likely to make our base the Westin, but are comfortable traveling a bit for the right experience.

Thanks!

Have you considered staying at Antigua, about 45min away? Stayed at Meson Panza Verde there. Definitely recommend it. There are also some nice places to stay on Lake Atitlan.