Laguna de Apoyo is a volcanic crater lake about 30 minutes from Granada, filling a caldera formed some 23,000 years ago. The water is warm, clear, and impossibly blue — fed by underground springs rather than rivers, so it stays clean and calm.
The lake is a nature reserve, ringed by tropical dry forest that descends steeply to the shore. Swimming, kayaking, and scuba diving are all popular — the lake is deep and home to several species of cichlid found nowhere else on earth. A handful of lodges and research stations line the shore, and the Estacion Biologica runs Spanish courses and volunteer programmes alongside its conservation work.
Most visitors come as a day trip from Granada or Masaya, though staying overnight is the better option if you want to catch the lake at dawn, when howler monkeys start up in the trees above the water.