If underground things(ancient, modern, all of them) appeal to you - there is a book "Underground" by Will Hunt you may enjoy. He doesn't explore Istanbul, takes

If underground things(ancient, modern, all of them) appeal to you - there is a book "Underground" by Will Hunt you may enjoy. He doesn't explore Istanbul, takes you on a tour of several other ancient ruins underneath modern day cities. If you're into that kinda thing, I recommend it.