As temperatures plummet in Harbin, China’s northeastern “ice city,” a group of swimmers eagerly prepares to take the plunge into freezing waters. Known as ice swimming, this daring winter tradition has been a part of the city’s culture for decades. Swimmers train year-round to build their endurance for the extreme cold.

In order to create a swimming pool in the Songhua River, participants break through a thick layer of ice, clear the pieces away, and strip down to bathing suits before entering the 10-meter-long pool. Despite the bitter cold—outside temperatures reach about minus 13°C and the water remains near freezing—these swimmers push through numbness in their limbs for the sake of the sport.

Chen Xia, a 56-year-old from Zhejiang province, has been winter swimming for 20 years. Despite having a cold, she bravely joined the others, strengthening her confidence. The freezing waters may cause her skin to feel like it’s being pricked with needles, but the joy she feels afterward keeps her returning year after year.

Winter swimming in Harbin dates back to the 1970s, inspired by Russian Orthodox religious baptisms. It officially became a sport in 1983, and today, Harbin is considered a “holy land” for winter swimmers. Swimmers believe the activity promotes good health, with some saying it prevents illness and boosts well-being.