Wooden Salt well Structure

The city of ZiGong(自贡)was a major salt produce in China. It also has the world's frist deepest drilled well, over 1100mters down in the ground, that was in the year of 1836(according to my memery). there are lots of those wooden structures left today around the city. They are called TianChe(天车). If you have a chance to visit ZiGong, These TianChe Site is a must-go...