Khorgo Uul Mongolia

With its surrounding lava field, this 200m-tall extinct volcano dominates the area to the east of the lake. From its west side there are stairs leading up to the rim of the crater, a short 15-minute trek that leads to fabulous views. Its desolate surrounds are littered with black volcanic rocks – making it look like it's erupted more recently than the estimated 10,000 years ago. Those with more energy, and a good sense of balance, could try climbing the slippery scree slope on the volcano's eastern side. You can then walk around the rim of the crater (anticlockwise is easiest) and climb down the steps. Sliding back down the scree sounds fun, but is pretty dangerous.