I am arriving in Tianjin on a cruise ship at 4am on the 4th of April. I fly out of Tianjin at 3.50pm that afternoon. If I left early(5am) would it be possible to train to Beijing and then on to the Great Wall in time to be back in Tianjin to catch my plane? Can you tell me which trains to get and how much this would cost? Would a taxi be a better option and what would you expect to pay for this service?