Most of Costa Rica is dominated by the Sierra Madre mountains, literally fractured into individual ranges and valleys by violent volcanic eruptions over eons of time.
, the country's most active one (cone-shaped Arenal
), located in the Tilaran Mountains erupts in some measure almost every day. To the southeast, the Poas, Barva, Irazu and many other volcanoes form the Central Mountain's most spectacular landforms, while the higher Talamanca Mountains front its southern border with Panama.
The heavily-forested northern plains (to the south of Lake Nicaragua
) stretch eastward along the San Juan River, then push southward through the rain forest edges of the Central Mountains, and on to the sandy beaches of the Caribbean coastline.
Costa Rica's beach-covered Pacific coastline is quite narrow, and indented with many small bays, as well as the Gulf of Dulce and the Gulf of Nicaya, both protected by hook-shaped peninsulas. In the west, those beaches rise abruptly into the coastal hills of the mountains.
Many dozens of rivers drain the land; the Chirripa, Frio, General, San Juan and Tempisque are indicated on the map above.