Kamchatka (Russia): Uzon Caldera
Another spectacular place you get to visit on your helicopter flight north to the Valley of the Geysers is the massive Uzon Caldera. This volcanic caldera is truly humongous and almost perfectly round 10km in diameter with an area of 150 sq km, surrounded by steep rock walls. There are five thermal fields with thousands of spouting hot springs and mud lakes and pools within the caldera. It’s a totally otherworldly landscape in every direction. Many pools in the caldera are bright red in color with extremophile micro-organisms surviving and flourishing in hot waters.