city, capital of Rondônia estado (state), western Brazil. It lies in the northwest corner of the state along the south bank of the Madeira River, a tributary of the Amazon, at an elevation of about 300 feet (100 metres). It was installed as the municipal seat in 1915. The head of navigation on the Madeira, Pôrto Velho serves as an important commercial, transportation, and communications centre. The city was the northern terminus of the now-defunct Madeira-Mamoré Railway, which was built to circumvent rapids between Pôrto Velho and Guajará-Mirim and to carry rubber from Mato Grosso state and northeastern Bolivia, the borders of which lie 100 miles (160 km) southwest. Tin ore and gold are mined in the vicinity. Lumber and medicinal plants and oils are also exported from Pôrto Velho, which has a commercial airport. Pôrto Velho is on the highway between Manaus to the northeast and Rio Branco to the west, in the Amazonas and Acre states, respectively. The city is also linked by highway with the city of São Paulo to the southeast, in São Paulo state. Pop. (2005 est.) 305,800.