Panmen Gate is the oldest city gate of Suzhou and the only existing water and land gate in China. The gate is located on the south-west corner of the Main Canal Suzhou. Originally built during the Warring States Period in the state of Wu, historians estimate it to be around 2,500 years old.It is composed of two water passages, three land passages and the outside gate. The canal outside the gate is the oldest section of the Grand Canal that was also built 2,500 years ago. In its vicinity, there is a 1,000-year-old pagoda named Ruiguang Pagoda, the earliest pagoda in Suzhou; and the Wu Bridge, the entrance to the gate at that time over the water passage and the highest bridge in Suzhou at the time.Panmen Gate is part of the ancient city wall (built in 514 B.C.) that surrounded and protected Suzhou. It was the only entrance through the wall to ancient Suzhou. The architecture of the wall is truly amazing.