American, via Brussels, traveling to Istanbul

Hello there, my name is Matt and I am from the U.S., and currently living in Brussels as an expat.

I am looking to take a weekend trip to Istanbul, and was curious if there are any americans that may be able to provide me any tips during my travels, or must see places that you highly recommend.

I am planning on staying at hotel from a worldwide chain (ie Sheraton, Hilton, Four Seasons).

Any insights on your experience there would be great!!

Regads,
Matt