International Day of Caves and Karst is being observed today, highlighting the importance of underground environments, groundwater, biodiversity, geological heritage and sustainable development.
UNESCO designated September 13 as the International Day of Caves and Karst, with 2026 marking the first-ever observance of the day following its proclamation by UNESCO in November 2025.
Caves and karst landscapes cover nearly one-quarter of the Earth’s land surface and provide drinking water to more than one billion people, making them important for global water security.
Caves are naturally formed underground spaces, while karst landscapes develop mainly through the dissolution of soluble rocks. These areas can contain caves, underground drainage networks and groundwater reservoirs.
According to UNESCO, caves and karst environments also contain unique subterranean biodiversity, geological records, and evidence of human history and culture.
The theme of this year’s observance is “Explore, Understand and Protect: Towards Sustainable Management of Caves and Karst.”
The first official international celebration is being held in Postojna, Slovenia, from September 10 to 13, featuring a scientific conference, educational activities, scientific excursions and events focused on sustainable management.
The International Union of Speleology has also encouraged countries and institutions to organize activities including cave visits, exhibitions, lectures and conservation programmes.
The observance emphasizes the need to explore, understand, protect and sustainably manage caves and karst systems, particularly because of their importance for water resources, biodiversity, science and cultural heritage.
