The unseen side of old Istanbul holds many treasures. A friend was taking me on a tour of the historical mosques of the city and we visited the Arab Camisi (Arab Mosque) situated on the Galata side of the Goldern Horn past the bridge. It's in a delightful part of the city filled with hardware shops and markets filled with tools and drills. The really interesting thing is that some of the places where these markets and shops are housed are astonishingly old.
Suleiman the Magnificent apparently sought to foster trade in this part of the city by building various commercial estates, places where traders and craftemen could work and sell their wares. On one of these walks through this area we stumbled across a two storey structure surrounding a cobbled courtyard with the characteristic Ottoman bricks and arches. Built in the 1540's It is still being used today as a place for blacksmiths and metal workers, it's wonderfully run down and overgrown.
The picture is of a water pump fastened to what I could only think was the base of an old Byzantine pillar.