Yakutsk is the coldest major city on Earth and is built entirely on permafrost.

Yakutsk is the capital of the Sakha Republic in Siberia and is home to over 350,000 people. It experiences a subarctic climate where the average January temperature is roughly -38.6°C. The city is famous for being the largest urban center built on continuous permafrost, which is soil that remains at or below 0°C for at least two consecutive years.Engineering in Yakutsk requires unique solutions because permafrost becomes unstable if the top layer melts. Most large buildings are elevated on reinforced concrete piles driven 10 to 15 meters into the frozen earth. This gap allows cold air to circulate under the building, preventing the structure's internal heat from thawing the ground and causing a collapse.The Melnikov Permafrost Institute, founded in Yakutsk in 1960, is a leading global authority on these conditions. Researchers there study the 'active layer' of soil, which is the top 1 to 3 meters that thaws during the brief summer. Because the ground below this layer is as hard as granite, traditional underground plumbing is impossible, leading to the city's signature network of insulated, above-ground pipes.Climate change poses a significant threat to the city's infrastructure as rising global temperatures cause the permafrost to degrade. Studies by the Russian Academy of Sciences indicate that ground stability in the region has decreased significantly over the last few decades. If the permafrost continues to thaw, the bearing capacity of the piles could fail, endangering thousands of residential and industrial buildings.