Subterranean River, Novosibirsk, Russia

It's an underground river in Novosibirsk, Russia. A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth (rivers flowing in canyons are not classed as subterranean).
Subterranean rivers may be entirely natural, flowing through cave systems. In karst topography, rivers may disappear through sinkholes, continuing underground. In some cases, they may emerge into daylight further downstream.