The first Caves and Karst Day: protecting nature below our feet

A new date for a largely hidden landscape

UNESCO identifies 13 September as the International Day of Caves and Karst. It lists the first celebration in Postojna, Slovenia, for 10–13 September 2026, including a scientific conference and official ceremony. These are the announced arrangements, not a report of completed outcomes or confirmation of an event in Bulgaria.

The observance brings together geological heritage, water and underground biodiversity. For a community interested in outdoor places, its value is the connection between what happens at the surface and an environment that is often out of sight.

Karst is more than a cave entrance

UNESCO describes karst as a landscape shaped by the dissolution of soluble rock. The US Geological Survey explains that these systems can contain interconnected fractures and conduits, alongside features such as springs, caves and sinkholes. The underground openings help explain why karst aquifers can be productive water resources while remaining particularly vulnerable to contamination.

That general mechanism does not let an observer map the destination of water from a particular hole. Establishing a local connection requires site-specific expertise and evidence. A visible entrance is one feature of a wider system, not a complete diagram of where water travels.

Choose a visit with a clear purpose

If you want to take part around 13 September, start with a managed visitor site, public talk or surface interpretation route. Confirm current opening arrangements directly with the operator, including booking, route difficulty, steps, footwear requirements and any seasonal restrictions. A date on an international calendar does not establish local access.

Ask the guide a question that connects the cave to the surrounding landscape: where does the site’s water come from, what is actually known about its route, and which surface activities require particular care? Ask how that knowledge was established. A good explanation should distinguish a mapped or measured connection from a plausible but untested one.

Make a surface observation useful

For a walk on an established, permitted route, keep a dated note of the place, the public information available and what you can observe without approaching openings or leaving the route. If there is visible dumping, photograph it from stable ground and pass the exact location privately to the site manager or responsible authority.

Describe what is visible rather than diagnosing pollution. The appearance of a spring cannot establish drinking-water quality, and a photograph of rubbish nearby does not prove contamination of a particular water supply. Leave sampling and interpretation to the responsible specialists.

• Use an established viewpoint; do not enter an unassessed opening to improve a photograph.
• Keep bottles, chemicals and cleaning water away from cave openings and sinkholes.
• Leave cave formations, animals and archaeological material undisturbed, and follow the site’s photography rules.
• Report unknown containers, buried material or waste inside a cave to the manager; do not turn the visit into an improvised removal operation.

Share the story without exposing a sensitive site

A public post can explain the landscape and link a managed visitor site without publishing coordinates for a sensitive entrance or wildlife location. Ask the manager what location detail is appropriate before sharing it. For an image, credit the photographer and obtain permission; an image on an event website is not automatically available for republication.

Keep access advice dated and specific. Record what the operator confirmed and when, and direct readers back to the operator for changes. If your account is based on a surface walk, say so rather than implying an underground survey.

A useful next step for a school or community group

Choose one question about the relationship between a managed cave and its surrounding landscape, then invite the site’s educator or a qualified specialist to explain the evidence. Combine that explanation with a permitted surface visit or a classroom discussion. The aim is to understand the place well enough to care for it, with a clear boundary between observation and specialist work.

Sources

• UNESCO: International Day of Caves and Karst

  Official observance date and announced inaugural programme in Postojna, 10–13 September 2026; also explains karst and the day’s purpose. Checked 10 September 2026. (LINK_ONLY)

• US Geological Survey: Karst aquifers

  Explains karst formation, groundwater pathways and vulnerability. General science background, not an assessment of a Bulgarian cave. Checked 10 September 2026. (LINK_ONLY)