Most of the tourist sites in China, such as the Ming tombs have concession tickets for the elderly over 65 or 70. Some places requires you to be 65, while some requires you to be 70 in order to qualify for 50% off the adult admission rate. If I remember correctly, the Ming Tombs offer 50% off for seniors above 65. Do remember to bring along your I.D. to prove your age.

Overall, I think it was a nice place to visit, but it will get extremely crowded in the underground palace. There were many local chinese visitors and most of them were quite rude and pushy. Do beware of your personal belongings as the locals have a very bad habit of pushing their way through instead of saying "excuse me".