The Qiantang River is 410 kilometers in length and is the longest river in the province of Zhejiang. Its soaring tides are a marvelous spectacle; only the Amazon River's surging tide can rival it! If you are visiting in September during the autumn equinox, you may be able to see one of the most unusual sights in the world. A tidal bore gathers momentum in the Gulf of Hangzhou, surges through the mouth of the Qiangtang River, and races up the river at a height of up to 30 feet and a speed of more than 15 miles per hour. In ancient times the governors of Hangzhou used to have arrows fired at these waves in an attempt to quell their destructive force. Nowadays more effective methods are used.