A series of volcanic mountain chains runs from the Nicaraguan border in the northwest to the Panamanian border in the southeast, thus splitting the country in two.The most north-westerly range is the Cordillera de Guanacaste, consisting of a spectacular chain of volcanoes. Further to the southeast is the Cordillera de Tilarán which includes the renowned cloud forest preserve at Monteverde and, just north of the main massif, the continually exploding Volcán Arenal(1633 metres), the most active volcano in Costa Rica.