Rondônia (pronounced [ʁõˈdoni.ɐ, ʁõˈdonjɐ] ) is one of the 26 states of Brazil, located in the northern subdivision of the country (central-western part). It is bordered by Acre in the west, Amazonas in the north, Mato Grosso in the east, and Bolivia in the south. Rondônia has a population of 1,815,000 as of 2021. It is the fifth least populated state. Its capital and largest city is Porto Velho, bathed by the Madeira River. The state was named after Cândido Rondon, who explored the north of the country during the 1910s. The state, which is home to c. 0.7% of the Brazilian population, is responsible for c. 0.3% of the Brazilian GDP. The state has 52 municipalities and occupies an area of 237,590.547 km2, equivalent to the territory of Romania and almost five times larger than Croatia. In addition to this, there are other important cities such as Ariquemes, Cacoal, Guajará-Mirim, Ji-Paraná, Rolim de Moura and Vilhena. Source: Wikipedia (en)