A paved road to the poisonous Horseshoe Lake

Horseshoe Lake is a high mountain lake at an elevation of 2.742m (8,996ft) above the sea level, located in the Mammoth Lakes area of Mono County, USA. There are carbon dioxide poisoning posted here.

How long is the road to Horseshoe Lake?

Located in California's Sierra Nevada mountains, the road to the lake is paved with some steep parts. It’s called Lake Mary Road. The lake is a popular recreation area and staging point for the Mammoth Pass and McLeod Lake trails. The drive is definitely worth it. Starting from the town of Mammoth Lakes, the ascent is 8.85 km (5.5 miles) long. Over this distance the elevation gain is 338 meters. The average gradient is 3.81%. The road is usually impassable in winters.

Is the Horseshoe Lake dangerous?

Set high in the Inyo National Forest, there’s a parking lot at the end of the road. Go early or go late to avoid crowds. It's said the lake teems with highly concentrated carbon dioxide and hydrogen sulphide, a toxic cocktail of poison, posing a threat to humans. If you start to feel faint, leave immediately. There are signs warning you of the dangerous gas being emitted. Because of this, camping in the area is not advisable. In dry years, as its feeder streams dry up, the lake diminishes dramatically over the summer, leaving expanses of sandy beach to play on.