The largest national park in all of Italy, Stelvio National Park provides the greatest chance to enjoy the height and breadth of the Alps this side of Switzerland. Because of its sheer size, there is more than enough to do for all manners of endurance level, interests, and abilities. There is not another park in Italy that boasts the sheer profundity of landscapes: from snowy mountain vistas to sweeping, grassy valleys to foaming waterfalls and plenty of ways of traversing in between.
Spanning three regions, the main access points in the Trentino region are Rabbi and Peio, while Castelbello grants access to the Alto Adige region, and Santa Catarina and Bormio to the Lombardy region. All of these towns are attractive in their own right and provide an idyllic mountain backdrop if you're in it just for a bit of serenity and relaxation. For others, it may best suit you to visit one of the many park offices and get a map of the myriad hiking trails and difficulty levels; the views are fantastic all over this park, so the fun is in getting to them.
For those looking to be awed, Ortler (3,905 meters/12,812 feet)and Königspitze (3,859 meters/12,661 feet) are two of the most epic peaks within the park, both of which are located near the center. Depending on the season, climbing expertise and at least two days time will be necessary in vanquishing these peaks. The aforementioned towns are close to many areas of exceptional beauty: the Pian Palu Reservoir and the thirteen staggering peaks of the Forni Glacier can be most quickly accessed from both Peio and Santa Catarina, while the lovely Val Zebru can be approached from Bormio, and skiing can be had within a stone's throw of any of them.
Possibly the most exciting proposition is a drive over the Stelvio Pass, the second highest paved road in the Alps. At 2,757 meters (9,045 feet), to call it winding or breathtaking would be a ridiculous understatement. Flirting with the border to Switzerland, it's worth renting a car (or a bike, believe it or not) to seeing the world from this elevation.
There's much more to see in Stelvio than we can touch on here. We suggest taking a look through the included websites to flesh out an idea of how this national park can figure into your plans.