The trek retraces the famous Trail K42 Italia race which follows paths well marked by the CAI of Rieti.
The K42 has two stopping points, Pian de’ Valli and the splendid city of Leonessa, it is possible, at discretion, to decide to start from one or the other to continue the route to the summit of Terminillo, these are the route details of the two variants:

• A: from Pian de’ Valli to Leonessa 23.4 km | 8.30 h – Difference in altitude ascent 1,138 m. – Descent height difference 1783 m.
• B: from Leonessa to Pian de’ Valli 23.8 Km | 8.50 h – Difference in altitude ascent 1,628 m. – Descent height difference 984 m.
  
  

Along the itinerary that starts from Pian de’ Valli, a mountain tourist resort in the central Apennines, a visit to the Church of San Francesco, a church Franciscan church which has the highest position in the world and inside which houses the relic of the body of Saint Francis and a majestic apse mosaic of 350 square meters, among the largest in Europe.
You descend towards Rifugio La Fossa, from here you can enjoy a splendid glimpse of the Cresta Sassetelli and the Valle degli Angeli. Going uphill towards the Acquasanta Source, the highest source in the Reatini Mountains area, you follow the ridge that leads, between woods and grassy plains, to the buttresses of Mount Tilia, the path passes a few tens of meters from the memorial stone of the disaster Terminillo plane, accident which occurred on 13 February 1955, where all 29 people on board perished, including the actress Marcella Mariani, former Miss Italy
Moving towards Leonessa you come across some of the 686 border crossings between the Papal State and the Kingdom of the Two Sicilies, some of which are well preserved, such as the one on the grassy plateau located shortly after the Fonte Petrinara refreshment point. And here is the steep descent that leads to Leonessa, and passes the Torre Angioina, an ancient military fortification erected in 1278 by Charles I of Anjou, the route continues reaching the historic center of the city of Leonessa, a suggestive medieval village which also features noble palaces dating back to the period from the sixteenth to the eighteenth century.
From the town you then travel along one of the most spectacular stretches of the entire route, the Dolomite-looking Cresta Sassatelli which leads to the summit of Monte Terminillo, where it is possible to contemplate the infinite, surrounded by mountains that extend to the horizon: the Massif of the Gran Sasso, Monte Velino, the city of Rieti and the entire Rieti Plain.
On the return journey, nature envelops you with its majestic trees, fresh air and breathtaking views, allowing you to fully enjoy the beauty of these uncontaminated places.