For hundreds of years, on the eighth month of the lunar calendar, people have gathered along the shores of China’s Qiantang River at the head of Hangzhou Bay to witness the waves of its famous bore tide. Higher-than-normal high tides push into the harbor, funneling into the river, causing a broad wave that can reach up to 30 feet high. If the waves surge over the banks, spectators can be swept up, pushed along walkways or down embankments. Below, I’ve gathered images from the past few years of the Qiantang bore tides.