Franconia has several regions with sandy habitats that are unique for south Germany and are protected as the so-called Sand Belt of Franconia or Sandachse Franken. When the Altmühlsee reservoir was built, a bird island was created and designated as a nature reserve where a variety of birds nest. Another important reserve is the Black Moor in the Rhön, which is one of the most important bog areas in Central Europe. A well known reserve is the Luisenburg Rock Labyrinth at Wunsiedel, a felsenmeer of granite blocks up to several metres across. The establishment of the first Franconian national park in the Steigerwald caused controversy and its designation was rejected in July 2011 by the Bavarian government. The reason was the negative attitude of local population. Conservationists are now demanding protection for parts of the Steigerwald by nominating it for a World Heritage Site. There are several nature parks in Franconia, including the Altmühl Valley Nature Park, which, since 1969, has been one of the largest in Germany.