Rio Segundo, abbreviated as Río 2º, is a city located near the geographical center of Argentina, built on the banks of the river Rio S…Rio Segundo, abbreviated as Río 2º, is a city located near the geographical center of Argentina, built on the banks of the river Rio Segundo about 40 kilometres east-southeast of Córdoba and about 660 kilometres west-northwest of Buenos Aires. It is the largest city of the Río Segundo County. Rio Segundo straddles National Route 9 and a main train line that runs from Córdoba to Buenos Aires. Pilar is a smaller city in size that resides on the other side of the river.