I just came back from my guided private tour with Odyssey Tours - it was great.
I suggest you do a 2 day overnight on the Great Wall. I did 2 separate day hikes and wish I would have done another. Odyssey Tours will do a great job setting up the transportation and give suggestions to the sites. I loved Jinshanling section of the wall
China Odyssey Touts are very flexible and accommodating. Send them an email with your requests and they will get back to you with what they suggest.
I would have taken this trip by myself except for the cruise. The great wall and terracotta soldiers are a must. But to have a guide is by far the best way to go. We had a private tour which helped a lot. Going single would still be a ball. there are so many things that we did not have time to do. I wish you the best.
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