Tenorio Volcano National Park is a national park in the northern part of Costa Rica, which forms part of the Arenal Tempisque Conservation Area. The jewel of the national park is the Tenorio Volcano, from which it derives its name. The volcano was made part of the National Park in 1995 and is located about 26 miles northeast of Fortuna in the Guanacaste Province. The Rio Celeste appears blue due to the emission of sulphur from the volcano and precipitation of calcium carbonate.