Kawah Ijen, or Ijen Crater Lake, is located in the southeast corner of Java. The trail is notoriously steep and the elevation quite high, meaning most hikers pause often to catch their breath. (At least we did!) The scenery leading to the sulfuric lake was jaw-dropping and surreal — all the exertion was well worth it. Due to all the sulfuric acid, the water’s pH is 0.5. Needless to say, swimming in the turquoise-colored lake was obviously not an option.
Nina Bhattacharya at Kawah Ijen, East Java