The northern lowlands constitute a 40,000-square-kilometer watershed drained by the Ríos Frío, San Carlos, and Sarapiquí and their tributaries, which flow north to the Río San Juan, forming the border with Nicaragua.

The rivers meander like restless snakes and flood in the wet season, when much of the landscape is transformed into swampy marshlands. The region is made up of two separate plains (llanuras): in the west, the Llanura de los Guatusos, and farther east the Llanura de San Carlos.

Today, tourists are flocking, thanks to the singular popularity of Arenal Volcano, and the fistful of adventures based around nearby La Fortuna.

These plains were once rampant with tropical forest. During recent decades much has been felled as the lowlands have been transformed into a geometrical patchwork of farmland. Yet, there’s still plenty of rainforest extending for miles across the plains and clambering up the north-facing slopes of the cordilleras, whose scarp face hems the lowlands.

Today, the region is a breadbasket for the nation, and most of the working population is employed in agriculture. The southern uplands area of San Carlos, centered on the regional capital of Ciudad Quesada, devotes almost 70 percent of its territory to dairy cattle. The lowlands proper are the realm of beef cattle and plantations of pineapples, bananas, and citrus.

The climate has much in common with the Caribbean coast: warm, humid, and consistently wet. Temperatures hover at 25–27°C year-round. The climatic periods are not as well defined as those of other parts of the nation, and rarely does a week pass without a prolonged and heavy rain shower (it rains a little less from February to the beginning of May). Precipitation tends to diminish and the dry season grows more pronounced northward and westward.

The Best of Costa Rica’s Northern Zone

• Thermal Springs and Spas
• Arenal Waterfall Gardens
• Arenal Volcano National Park
• Rancho Margot
• Arenal Rainforest Reserve
• Caño Negro Wildlife Refuge
• Tenorio Volcano National Park
• Centro Neotrópico Sarapiquís
• Selva Verde
• Isla Las Heliconias