The forum has been invaluable for getting my bearings before I visit. We were thinking doing a tour just one day (we have 4 days in Istanbul total) in old city but so many of you say its not necessary because primary sites - Blue mosque, Hagia Sofia, Topkapi Palace, Basilica Cistern and the Grand Bazaar are basically clustered close to each other and its pretty easy to find your way around. My question is however - is there information provided at each of these sites relating to the historical significance of each, do some sites have guides at the site (such as at the Palace), or do you just wander around? I have bought a guidebook that describes each, but I don't always feel like pulling out a book. I see many comments that the tours do too much in one day, so basically are rushed.