Tabatinga is a city in the north-western part of the state of Amazonas in Brazil. It forms a contiguous settlement with the Colombian town of Leticia. Santa Rosa on the nearby island in the river is in Peru.
Movement between all three countries' border towns is unrestricted; but of course, make sure you're stamped into the correct country if leaving the border area. Try to minimize the amount of times you go through immigration: i.e. if entering the region from one country and leaving from another, just get one exit and one entry stamp - even if you visit all three towns in this area. Anything more seems to annoy the immigration officers.
The Brazilian immigration office is located some way down Tabatinga's main avenue, Avenida da Amizade.
The Colombian immigration office is at the airport, so if you're flying in and moving on to a different country you may as well get an exit stamp when you land. Don't wait several days between getting your exit stamp and the next entry stamp; however leaving it one day doesn't cause any problems.
The Peruvian immigration office in Santa Rosa is fairly central and easy to find, just ask someone.
All three currencies are generally freely traded in the town, though Peruvian Soles may not be willingly received. Changing money is not difficult though.
"Fazendinha", where there´s good pizza!
"Tres Fronteiras" restaurant has a beautiful garden and a romantic atmosphere. They specialize in BBQ and Peruvian food and are known as the best restaurant in Tabatinga.
"Vinicius" bar, on the main street.