Puerto Maldonado is a small town in the Peruvian Amazon on the Madre de Dios and Tambopata rivers. As such it is the jumping off point for river trips or stays in lodges in the jungle.
It's quite easily accessible either by air or by a spectacular 10 hour bus trip from Cuzco. The town is friendly and has some good eating options. If you stay in the town, make sure you take a trip to Sandoval lake or just a trip down one of the river tributaries. The whole place has a real jungle feel and is much less of a big city experience unlike Iquitos or Manaus.