"Laguna Caliente" – Parque Nacional Volcan Poás, Alajuela Province, Costa Rica

Rising up to 8,885 ft (2,708 m), Poás remains one of Costa Rica's largest and most active volcanoes. Walking just 15 minutes from the visitor's center, the main crater supplies guests with a spectacular view. At almost a mile in diameter (1.6 km), the crater’s rain-fed sulfuric pool still bubbles and emits smoke into the air, reminding you of its imposing activity.

There are two crater lakes near the summit. The northern lake is known as the Laguna Caliente ("hot lagoon") and is located at a height of 2,300 m in a crater approximately 1.7 km wide and 290–300 m deep. It is one of the world’s most acidic lakes. The acidity varies after rain and changes in volcanic activity, sometimes reaching a pH of almost 0; consequently, it supports little or no aquatic life. The bottom of this lake is covered with a layer of liquid sulphur. Acid gases create acid rain and acid fog, causing damage to surrounding ecosystems and often irritation of eyes and lungs.