Described by the Spaniards as the gates of hell, the craters that comprise Volcán Masaya National Park are the most easily accessible active volcanoes in the country. There are two volcanoes, Masaya and Nindirí at the park, which together comprise five craters. Of these, Cráter Santiago is still quite active, often smoking and steaming.
From the summit of Volcán Masaya (632m/2073ft), the easternmost volcano, you get a wonderful view of the surrounding countryside, including the Laguna de Masaya and town of Masaya beyond. The park has several marked hiking trails, many of which require a guide. These include the lava tunnels of Tzinancanostoc and El Comalito, a small steam-emitting volcanic cone.
The park entrance is just 6km (4mi) from Masaya on the Managua highway. You can get there on any Managua-bound bus from either Masaya or Granada. They'll give you a map and guide. Don't miss the Plaza de Oviedo, a clearing by the crater's rim named after the 16th-century Spanish monk who, suspecting that the bubbling lava was gold, descended to the crater with a bag and a pooper-scooper and came back alive. Here, the smell of sulphur is strong, and it's easy to imagine Lucifer lurking in the depths below.