The hike up Diavolezza is an amazing and beautiful hike with incredible vistas of several different glaciers. The hike begins and ends at the Bernina Diavolezza train station. There is a large parking lot here for the cable car station.
From the train station, follow the yellow signs toward Diavolezza. The hike leads up a gravel road for 1.2 miles. Here you will pass a small yellow hiking sign. At this point you can continue up the shorter path along the gravel road or take the prettier but longer and slower trail to the left. The trail is marked with red/white blazes.
Shortly after the trail and road rejoin you'll pass the alpine lake Lej da Diavolezza on your right. From here the trail becomes more technical. There are a few steep sections secured with chains and wooden steps. As you approach the top, you will have to negotiate several snow fields (even in late summer). Some of these are quite steep, so be prepared.
When you reach the trail intersection at the top at 4.5 miles you will see another yellow sign. Here you have a few options. To the left is Sass Queder, a small peak that takes only about 45 to 60 minutes round trip (out and back). Sass Queder has great views in all directions. Piz Torvat obscures some of the glacier, but the southern peaks are still magnificent. Sass Queder also has a few benches and a small fire pit for cooking (though you'll have to carry fuel there somehow).
To the right (west) from the intersection, the Diavolezza Bergstation is only a 10-minute walk away. Farther to the right (west) is Munt Pers, which is about 2 hours round trip (also an out and back, 1.6 miles each way from the Bergstation). Munt Pers has fantastic views of the surrounding peaks in all directions. It is also one of the highest hiking trails in all of Switzerland (excluding alpine routes), reaching 3,207 meters (10,521 feet). The trail is very rocky and somewhat technical, but no climbing or scrambling is necessary. From the top the views are absolutely phenomenal in every direction, from the Morteratsch Glacier to the Piz Bernina and Piz Palü to the northern peaks. It is breathtaking!
If you have the equipment, there is also a popular via ferrata route that runs up Piz Trovat. You can find more information here.
After your time at Diavolezza, the hike simply returns down the same path as the ascent. One possible modification is to head back via Lej d' Arlas and end the hike at Bernina Lagalb instead. For more information, consult the official Swiss online map.
If the hike is too long for one day, you can shorten it by taking the Diavolezza cable car up or down. You can also split your hike into two days and stay overnight at the Berghaus located at the Diavolezza Bergstation. Take note that, unfortunately, the station does not have free drinking water for hikers, so you'll have to buy bottled drinks at the restaurant.
Enjoy the hike to Diavolezza and Munt Pers!