If you do one thing in Istanbul, you must visit Topkapi Palace, where the Sultans lived until the mid 1800s, when another palace was built (unfortunately, I missed that one!) We hired a "state licensed guide" (it said so on a sign he wore around his neck!) who for $30 gave us a complete two hour tour of the palace.
The Harem, or the residence of both the Sultan and his women, was fascinating! According to our guide, the women of the harems had it pretty good - it was apparently a great honor to be part of the sultan's harem, and many young girls aspired to this. And why not? Some of them had great quarters, nice baths, a swimming pool, Unics at their beck and call - and all they had to do was pleasure the Sultan once in a while. Okay, I know it's not that simple! There was a clear hierarchy in the harem, with the Sultan's mother in the position of power, the mother of the Sultan's first boy was second, and the Sultan's favorites had a pretty nice life as well. The others helped serve them.
Another awesome and interesting part of the palace was the was the treasury, which held a ton of jewels (literally!) Most of these treasures were gifts for the Sultan. The treasurey also holds a pretty amazing relic - the skull of John the Baptist! I wasn't too sure about how they got a hold of this, but there it was. The other pieces were amazing, too! It's a must!
If you're not too hungry, I'd skip the restaurant there. Although it's convenient and has great views of the Bosphorus, the food was overpriced and not all that great.