These unusual miniature sheets require special glasses with red and cyan filters. The anaglyph image contains information for both eyes but different colour filters on each eye block some from reaching the left eye and some from the right eye, which creates a stereoscopic or three dimensional effect. The Calcite Crystal Museum is in Fertőrákos, a village located in Lake Fertő cultural landscape, which is on the World Heritage list. The protected private collection presents the mountains of Hungary and their sedimentary, igneous and metamorphic forms of rock through two thousand calcite crystals of different colours and shapes, and four hundred fossils. This collection, the only one of its kind in the world, is part of Hungarian National Cultural Heritage. A few precious pieces from the collection of the Calcite Crystal Museum in Fertőrákos can be seen on the stamps. The new stamp is released as a single stamp and also as a miniature sheet containing four stamps. It is being issued simultaneously with another stamp and miniature sheet in the Treasures of Hungarian Museums series, the Lamp Museum, Zsámbék. The two miniature sheets are also available as a 3D set. The set in an A5 film-wrapped pack consists of a copy of each of the two different special miniature sheets with information in Hungarian and English, and a gift pair of 3D glasses. Source: esestuske.geo.info.hu, kalcitkristalyok.hu/index.html