Tao-Rusyr Caldera

Tao-Rusyr Caldera is a volcanic crater basin on Onekotan Island in Russia's Far East, spanning several kilometers across the southern part of the island. The sunken center holds Kol'tsevoe Lake, a deep mountain lake ringed by steep rock walls.

The caldera formed when a massive volcanic eruption thousands of years ago released enormous volumes of rock and magma from below. This violent collapse shaped the deep basin that now holds the lake and remains a prominent feature of the island's landscape.

The Russian Navy's influence on regional geography led to naming the central peak after Captain Pyotr Krenitsyn of the Imperial fleet.

The site sits in a remote location and is difficult to reach on your own, so most visitors join organized tours to explore the area safely. Summer months offer the best conditions for travel when weather is more stable and access is easier.

At the center of the lake rises a symmetrical cone mountain that appears as an island within the water, with its own crater at the summit. This formation makes the caldera a rare example of a mountain within a mountain structure in this remote corner of the world.