Cornu is a commune in Prahova County, Muntenia, Romania. It is composed of three villages: Cornu de Jos, Cornu de Sus, and Valea …Cornu is a commune in Prahova County, Muntenia, Romania. It is composed of three villages: Cornu de Jos, Cornu de Sus, and Valea Oprii; the administrative centre is Cornu de Jos. The commune is located in the northwestern part of the county, next to the DN1 road that connects it to the county seat, Ploiești and to the capital, Bucharest, and to Brașov.