I too will emphatise that the taxis are very safe. I'm writing this too since I will say that I am a woman and was travelling alone. No problems.

The idea to have all addresses written down is very good advice. If you speak German, it can help more than English sometimes.

Also, just want to recommend taking one of the government boats up the Bosphurus. You can get off at the last stop in Andalou Kavagi and hike up a hill to some ruins and get a totally fab view of the Clashing Rocks and the entrance to the Black Sea. Total Cost about 3MM TL (about $3)

Have a great trip. I wish I were headed back over there soon.

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I wish I were 1,000 miles away