The Reventazón River, Rio Reventazón,, is a river in Costa Rica. Reventazón River forms part of the Reventazón-Parismina drainage basin, it is 145 kilometres long and flows into the Caribbean sea. It starts at the base of the Irazú Volcano, passing through the east side of the Central Valley, and flows through the Orosí and Turrialba Valleys. After reach…The Reventazón River, Rio Reventazón,, is a river in Costa Rica. Reventazón River forms part of the Reventazón-Parismina drainage basin, it is 145 kilometres long and flows into the Caribbean sea. It starts at the base of the Irazú Volcano, passing through the east side of the Central Valley, and flows through the Orosí and Turrialba Valleys. After reaching the Caribbean coastal plains it joins the Parismina River and forms what is called the Reventazón-Parismina.