There’s a place in Siberia that the locals call “The Gateway to Hell.”

Technically, it’s a retrogressive thaw megaslump. In plain English, a crater melted into the permafrost. In fact, it’s the largest permafrost melt in the world.

It began 60 years ago, when the Russians clear-cut a strip of Siberian forest. This exposed the soil to the summer sun, which began to melt a crater that’s now a half mile wide and 300 feet deep—and still growing.

This is important for two reasons.

First, the crater has exposed 650,000 years of previously hidden sediment.

In winter, when the soil is frozen and stable, scientists can enter the crater to recover specimens of extinct animals and to study how cycles of forestation and changing climate have impacted the area over millennia.

Second, in summer, when the permafrost is melting, scientists are able to measure the air above the crater.

As the organic material thaws, it’s consumed by microbes, which produce CO2 and methane. The crater produces both of these greenhouse gases at twice the rate of the surrounding area.

Forest fires have exposed other areas of Siberian soil to the sun. And summer temperatures are rising. Both are melting more permafrost.

The Gateway to Hell provides scientists a laboratory to study that melting, to see how it may affect the local landscape, and global climate, in the future.