We even had 2 tours with "open tours". The booked tour was only possible one day later (we were lucky that our schedule allowed it) and we got a second tour to the NY suburbs for free as an excuse. Both were excellent. This was mainly due to our guide Stephan. He just knew EVERYTHING. He also had tips for activities that you can't find in any travel guide or on the Internet. Our "German-American" was also easy to understand and he knows both cultures.