Grænavatn (Greenlake) is a volcanic crater that got its name from its unusual green color. The color is due to a high level of sulphur in the water and its depth. The lake is only about few hundred meters in diameter. For a small lake it is quite deep, though, or 45 meters. This is visible as you stand by the brim, and you can see how the color changes by the shoreline where the lake gets deeper. Grænavatn is considered by geologists to be one of the most noteworthy geological phenomena of its kind in Iceland.
Krýsuvíkurkirkja was built in 1857, rebuilt in 1964 and then went into the custody of the National Guard and was added to the list of listed houses. The altarpiece of the church was a painting by Svein Björnsson, a painter. Krýsuvíkurkirkja was used as a parish church until 1910. It was demolished in 1917 and used as an apartment from 1929, but then again turned into a church in 1963-64 with the help of Björn Jóhannesson, former mayor of Hafnarfjörður, but Hafnarfjörður moved the building to the National Museum in the autumn of 1964. A church will have been built in Krýsuvík at the beginning of Christianity in this country in Kirkjulág in Húshólmur before Ögmundarhaun flowed in the middle of the 12th century. After that event, the church was relocated. The church that burned was built by Beinteinn Stefánsson, a tenant farmer in Krýsuvík, from driftwood in 1857. The settlement in Krýsuvík was abandoned at the beginning of the last century and in 1929 Krýsuvíkurkirkja was abolished as a sanctuary. Magnús Ólafsson, who last lived in Krýsuvíkurbær, stayed in the church for years as a good shepherd. Extensive repairs began in 1986 and were then restored to their original form. The outer walls had tarred artwork and corrugated iron on the roof. No old church objects had been preserved and the pews, altar and pulpit were of a new and simple type. It burned to cold coals on the eve of January 2, 2010. Two boys and two girls aged 17-20 confessed to setting the church on fire, but the church was completely destroyed in the fire. The youths poured gas cans inside the church and lit them. They then left the place but also brought with them small coins that they stole from the collection of Krýsuvíkurkirkja. During questioning by the police, it was revealed that they were going to set fire to a church, but it seems to have happened by chance.