International Day of Caves and Karst2026 · Date · History · Messages · Quotes
About International Day of Caves and Karst
The International Day of Caves and Karst is observed on 13 September. UNESCO proclaimed the Day to increase awareness of caves and karst landscapes, their scientific and cultural value, their biodiversity and their importance for water resources.
Karst develops where soluble rocks are dissolved over long periods, producing features such as caves, sinkholes, underground drainage and springs. Because water can move rapidly through these systems, pollution and land-use decisions can have unusually direct consequences.
Why International Day of Caves and Karst matters
Caves and karst preserve geological records, archaeological evidence and specialized ecosystems while also supplying drinking water to large populations. Their value therefore crosses geology, hydrology, biodiversity, culture and sustainable development.
The Day encourages research, education, protection and international cooperation while drawing attention to the fact that underground environments can be fragile and difficult to restore after damage.
History of International Day of Caves and Karst
The International Union of Speleology developed the initiative, and the Republic of Slovenia formally submitted it to UNESCO with broad international support.
At its 43rd session, UNESCO’s General Conference adopted 43 C/Resolution 26 on 12 November 2025 and proclaimed 13 September of each year as the International Day of Caves and Karst.
The UIS proposal explains that 13 September also recalls the date in 2021 when caves and karst were presented at UNESCO during the International Year of Caves and Karst campaign.
UNESCO states that the first celebration will take place in Postojna, Slovenia, from 10 to 13 September 2026, with the formal annual Day on 13 September.
How the observance developed
This timeline uses documented milestones from reviewed sources. Missing stages are left out rather than guessed.
International Year of Caves and Karst campaign
The international-year campaign preceded the permanent UNESCO Day and helped build the advocacy and institutional network behind the later proposal.
Republic of Slovenia, following a proposal developed by the International Union of Speleology (UIS)
The Government of Slovenia says Slovenia officially submitted the initiative at the proposal of the UIS; UIS documents its earlier development of the proposal.
UNESCO General Conference
43 C/Resolution 26
First documented observance
UNESCO’s official page states that the first celebration runs 10–13 September 2026 in Postojna, with 13 September as the proclaimed annual date.
UNESCO
The resolution assigns promotion of the celebration through UNESCO, and UNESCO maintains the official Day page and first-celebration programme.
What the evidence establishes
Confirmed institutional roles and milestones are shown first. Details that could not be established from the reviewed sources are listed separately below.
2 fields not established in reviewed sources
Predecessor and precursor observances
Earlier or merged observances are kept separate from former names and later institutional actions.
Also known as
International Day of Caves and Karst, Caves and Karst Day
How to Observe International Day of Caves and Karst
Learn how a local karst aquifer works and why pollutants can travel differently through karst than through many other groundwater systems.
Support cave visits only through responsible operators or protected-site rules that limit damage to formations, wildlife and archaeological deposits.
Use geological surveys, UNESCO-designated-site material or speleological organizations to explain cave formation and conservation accurately.
Highlight the links among groundwater protection, biodiversity, scientific monitoring and land-use planning in karst regions.
International Day of Caves and Karst Facts
The Day is observed on 13 September.
UNESCO established it through 43 C/Resolution 26 in 2025.
The initiative was formally submitted by Slovenia following work by the International Union of Speleology.
UNESCO says the first celebration takes place in Postojna, Slovenia, in September 2026.
The 13 September rationale is connected to the 2021 International Year of Caves and Karst campaign at UNESCO.
International Day of Caves and Karst Messages
May International Day of Caves and Karst inspire curiosity about the living world and thoughtful action to protect it.
Celebrate International Day of Caves and Karst by learning from credible conservation sources and choosing one practical way to reduce harm or support protection.
Wishing everyone marking International Day of Caves and Karst a day of discovery, respect for nature and care that continues beyond today.
On International Day of Caves and Karst, may appreciation for the natural world lead to informed stewardship and practical care for the places and species around us.
International Day of Caves and Karst Quotes
“Caves and karst landscapes cover nearly a quarter of the Earth's land surface and provide drinking water to more than a billion people.”
Topic and context
What this page does not assume
- Keep the source-defined country, community, organizer or institutional scope; do not silently broaden it.
- Do not treat the title alone as proof of government recognition or public-holiday status.
- Do not add a creator, founding story or origin claim unless the supporting evidence establishes it.
Evidence & sources
Sources used across the guide are gathered here. Labels show how each source supports the page, and contextual references are kept separate from primary evidence.
UNESCO Records of the General Conference, 43rd session, Volume 1: Resolutions (opens in a new tab)
Government of Slovenia — UNESCO proclaims International Day of Caves and Karst (opens in a new tab)
International Union of Speleology — proposal history and 13 September rationale (opens in a new tab)
UNESCO — International Day of Caves and Karst (opens in a new tab)
Dedicated Authoritative Page
Understand it, compare it, then explore further
Start with the most common factual questions, then compare closely related observances and explore useful connections.
Frequently asked questions
When is International Day of Caves and Karst?
13 September The documented recurrence rule is: 13 September.
Does International Day of Caves and Karst fall on the same date every year?
Yes. It uses a fixed annual date unless stronger evidence changes the pattern.
Is International Day of Caves and Karst an official public holiday?
The reviewed sources verify it within this scope: UNESCO international day. That recognition does not by itself make it a statutory public holiday; the site only makes public-holiday claims when reliable evidence explicitly does so.
Who established or recognizes International Day of Caves and Karst?
The reviewed sources identify UNESCO General Conference as the proclaiming or establishing body. The proposer or originator is recorded separately as Republic of Slovenia, following a proposal developed by the International Union of Speleology (UIS). Current facilitation or coordination is recorded as UNESCO.
Is International Day of Caves and Karst international or country-specific?
The documented scope is international or global: UNESCO international day. That does not mean every country treats the date as a public holiday or observes it in the same way.
How is this page verified?
The factual information is checked against reviewed sources, including the date pattern, scope and institutional history. This page was checked on 2026-09-05.
When is the International Day of Caves and Karst?
It is observed every year on 13 September.
Who proposed the Day?
The International Union of Speleology developed the initiative, and the Republic of Slovenia formally submitted it to UNESCO.
When is the first celebration?
UNESCO identifies September 2026 as the first celebration, centered in Postojna, Slovenia, with the annual Day on 13 September.
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