San Martin is a region located at the northern portion of Peru and is part of the Upper Amazon. To get to the area, you could fly from Lima to Tarapoto. Tarapoto is the commercial center of the region. The interesting parts for travelers would be 30-minute to an hour’s travel away from the center of this city.
I was able to visit San Roque de Cumbaza, a village in the district of Lamas, but is reached via another road from Tarapoto. The center of Lamas is worth visiting, too.
A visit to Tingana is what you should do if you are in the region. You would have to go to Moyobamba first. (Moyobamba is the region’s political capital.)