To trek the Kuari Pass and other routes in Nanda Devi Sanctuary, you need a permit and a registered guide (per day ₹1000 to ₹1500). There are excellent operators in town who can organise everything, including further-flung and intensely adventurous multiday expeditions.
Roopkund Trek: Skeleton Lake
One of India's more unique treks is the three- to four-day journey up to Roopkund lake, which culminates with the macabre sight of 9th-century skeleton remains that sit at the bottom of the glacial lake. Stumbled upon by a game-reserve ranger in 1942, some 300 bodies were discovered in the shallow lake, perched at the dizzying altitude of 5029m. After decades of debate as to their origins, in 2013 scientists concluded the remains dated from nomadic 9th-century tribespeople, who were believed to have perished in a fatal hail storm.
Today only scatterings of bones and skulls remain; many have been stolen or shifted for research purposes, and they're generally only viewable for a month or so between late June and middle of September; other times they're covered in snow and the trail is inaccessible.
Regardless of the skeletons, it's one of the region's most spectacular treks. While the 2018 camping ban in the bugyal (high-altitude meadows) by the Uttarakhand high court has seen it scaled back from what's usually a six- to eight-day trek (check to see if this has been overturned), the trip takes you through the same varied landscapes of oak and rhododendron forests, pristine alpine bugyal and life-affirming Himalayan views.
The base camp begins in the village of Wan (2400m) in Chamoli district. It's not a trek for inexperienced hikers, and you'll need to arrange a permit. A guide is highly recommended – best arranged through the trekking companies in Joshimath.