There are several beautiful palaces and mosques in Instanbul--the Blue Mosque
is one, the Tapati(sp)Palace is another. If you have time a visit to the Market
is most interesting--be sure you don't get lost. A good suggestion is to check
with your library and peruse one of the travel books on Turkey.
i was in istanbul a few years back for a few days and i suggest seeing the topkapi palace (a bunch of neat stuff there - like jewels and even a hair that was supposedly plucked from muhamad (and his footprint)).
Also, stop and see the grand bizzarre (mostly covered - so that is nice in the hot summer). Also see the spice market (by the water) if that is your thing. I liked the blue mosque and the st. sophia mosque (reddish color) (in the evenings they have a history show right outside the st. sophia mosque - each day is a different language).
If you are a female - be careful about wearing shorts - best idea is to wear conservative clothes.
they sell water and food in venders all over the city that is less than american standards & i got very sick after eating/drinking some of this - i suggest sticking to ship food/water or very reputable places.