MoscowFlow runs an artificial CityWave pool in Moscow, Russia, and it's one of the stranger entries on this list given what else is packed into the building — including an indoor skydiving wind tunnel under the same roof. The standing wave itself is forgiving enough for intermediate surfers to drill turns without a river anywhere nearby, and since it's fully artificial it runs regardless of season or weather. Expect an entrance fee and a crowd mixing first-timers with regulars working on technique. It's less about raw performance surfing and more a fun, convenient fix when the real rivers are frozen or just too far away.