From the Mountain Residence Montana you can ride along the main road or bicycle path to Preindl. There the first climb towards Frondeigen begins. At the top, the descent towards Wahlen begins (where you also reach the actual Dolomiti Superbike route). From there you continue towards Dobbiaco. Continue, slightly uphill along the bike path towards Dürrensee. Shortly after the Dürrensee the actual ascent towards Prato Piazza begins. Via Prato Piazza to the descent towards Villabassa and from there to the last ascent, partly along the Roman Path, back to Frondeigen. From there back down into the Casies Valley and back to the Mountain Residence Montana.
If this variant is too long for you, you can take the car to Villabassa and start the original route with the ascent to Frondeigen. Find below the GPX data for both variants.
Starting points: Mountain Residence Montana (Village square Villabassa)
Track length: 78km (60km)
Vertical ascent: 2751m (1570m)
longer option with start at Mountain Residence Montana
Original route 60km with start at Villabassa