Southeast of Trento in the village of San Martino di Castrozza, the San Martino Bike Arena has tons of flow trails and downhill trails to explore. The Valsorada XC Trail starts at the summit of the Tognola Gondola and drops into the Valsorada forest over bridges and wooden walkways. Then, it you can follow either Trail #344 or Trail #390 back down into San Martino. There is bus service from surrounding villages and also withing the town of San Martino.
The San Martino di Castrozza ski area part of the Dolomiti Superski region which has over 1,200km of pistes spread over 12 valleys that served by 450 lifts. While a single skipass gives access to the Dolomiti Superski region, keep in mind that the 12 valley are not all interconnected and you may need bus transport between valleys. Also, the snowfall in this southernly ski region is known to vary greatly season to season. Keep in mind that there is limited off-piste snowboarding in the Dolomiti Superski region -- it is prohibited in most areas and guides are highly-recommended in the others.
Overall, San Martino Bike Arena is the 44th most popular mountain bike trail of all 45 mountain biking rides in Italy.