An approximately 5-metre-tall stalagmiteStalagmite growth is extremely slow. For 1 mm to grow, it usually takes decades, for 1 cm, centuries and for a stalagmite of several metres… try to figure it out yourself!. The 'Brilliant' stands in a spot with a strong and even drip from the ceiling. A thin layer of pure calcite sinter is deposited constantly and evenly by the water trickling down the rounded crown of the stalagmite. That is why it looks so extremely white and shiny, and it is not surprising that it has been the symbol of Postojna Cave and the Slovenian Karst for decades. A pillar stands next to it in true baroque splendour.
The creator of all these wonders is sinter, a mineral, usually calcite, deposited by supersaturated water. Sinter builds stalagmites, wall linings, pools, crusts and other fantastic forms in karst caves. In the background of the 'Brilliant', the walls of the hall flaunt sinter curtains and a sinter fountain called the Organ, with tiny stalactitesStalagmites grow from the ground while stalactites grow from the ceiling in the form of tubes. When the two formations join, they make a pillar. hanging from the ceiling. This is definitely one of the beautiful sights in the sinter-rich part of Postojna Cave.