Tianmen (天门山) is a famous mountain, located near Zhangjiajie City in China's Hunan Province. Before we were allowed to walk on its glass walkway, we had to put red slippers on over our shoes. Unfortunately, I couldn't stretch the tiny slippers over my hiking boots. Two months before this, a similar glass bridge on Yuntai Mountain (云台山) cracked shortly after opening. Officials claimed that even though the glass was cracked, it “will not pose threat to safety.”