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 southern Nicaragua.

The rivers meander like restless snakes and commonly 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 new roads and the singular popularity of Arenal Volcano, the catalyst for a burgeoning adventure industry based in La Fortuna. Skirting the foothills of the cordillera, the vistas southward are as grandiose as any in the country. From below, Costa Rica’s ethereal volcanic landscapes remind me of Bali. Pastures tumble down the mountainsides like folds of green silk. The plains are thick with chartreuse wands of rice.

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 is 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. The entire border zone with Nicaragua is also an agrarian front in the battle to establish the Si-a-Paz transnational park.

Today, the region is a breadbasket for the nation, and most of the working population is employed in agriculture. The southern uplands of San Carlos, centered on the regional capital of Ciudad Quesada, devotes almost 70 percent of its territory to cattle and produces the best-quality milk in the nation. In the lowlands proper, dairy cattle give way to beef cattle and plantations of pejibaye palm and 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

• Caño Negro Wildlife Refuge
• Tabacón Hot Springs
• Arenal Volcano National Park
• Rancho Margot
• Arenal Rainforest Reserve
• Centro Neotrópico Sarapiquís
• Selva Verde
• Heliconia Island