The word “karst” — the geological phenomenon of limestone carved by water — comes directly from the Slovenian “Kras”, the region in the country's south-west. Slovenia counts more than 14,000 registered caves, but visitors almost always face the same question: Postojna or Škocjan? After dozens of accompanied visits since 2004, here is the honest comparison to settle it — 2026 prices verified — plus the secret caves the coach parties never see.
The short answer
- With children or grandparents: Postojna. The little train does 80% of the work, and the visit works from age 3.
- To be blown away and skip the crowds: Škocjan. The UNESCO-listed underground canyon is one of Europe's most staggering sights — rawer, wilder, half the visitors.
- You have a full day: do both — they are 40 minutes apart. Škocjan in the morning (first tour at 9 am), Postojna and Predjama Castle in the afternoon.
- You've already done both: Križna jama and its rowing boat across underground emerald lakes — the most magical cave visit in the country, and almost nobody goes.
Postojna vs Škocjan: the 2026 comparison table
| Postojna | Škocjan | |
|---|---|---|
| Adult price 2026 | €34.90 (€49.90 with Predjama) | €24 in summer, less off-season (children €12.50) |
| Duration | 1.5 h, including 3.7 km by little train | About 2 h on foot, plenty of stairs |
| Style | Spectacular and comfortable: giant formations, careful lighting | A 146 m-deep underground canyon, a vertiginous bridge — raw and grandiose |
| UNESCO | No | Yes, since 1986 |
| With children | From age 3; no pushchairs, but baby carriers work | Better from age 6; good shoes essential |
| Temperature | A constant 10 °C — bring a fleece, even in August | A constant 12 °C |
| Photos | Allowed without flash | Forbidden inside |
| Crowds | Very heavy in summer: Europe's most visited cave | Moderate, guided departures at fixed times |
| Booking | Advisable online in summer, timed slots | Recommended in high season; arrive 30 minutes early |
Postojna Cave: the international star
It is the most visited cave in Europe: 24 km of galleries, 5 km of them open to the public. The visit starts with a ride on the little electric train — a tradition since 1884 — that plunges nearly 4 km underground before a guided 1.5 km walk among spectacular formations, including the famous “Brilliant”, a five-metre stalagmite of white calcite. You will also meet the strange olm, the blind “baby dragon” that can live a century and fast for a decade. Audio guides come in 17 languages.
The adult ticket costs €34.90 in 2026, and the combined ticket with Predjama Castle €49.90 — the right call if you stay the afternoon. Book a timed slot online in summer: the 11 am queue in August is the most faithful snapshot of Slovenian overtourism. The site sits just off the A1 motorway, 45 minutes from Ljubljana — our Postojna page covers access and the surroundings.
Škocjan Caves: the shock (UNESCO)
If Postojna is the star, Škocjan is the secret. World Heritage-listed since 1986, these caves don't try to charm you: they crush you. The Reka river has carved a 146-metre-deep underground canyon that you cross on the Cerkvenik Bridge, suspended 45 metres above the roar of the water — one of the most memorable moments you can live underground in Europe. No photography is allowed inside, and rightly so: everyone just looks.
Count on about 2 hours of guided visit on the main “Through the Underground Canyon” route (€24 in summer, €12.50 for children), with real staircases — wear proper shoes. From April to October a second route, “Following the Reka River”, follows the downstream section in daylight. Departures run at fixed times (9, 10 and 11 am, then 1 to 4 pm in summer): arrive 30 minutes early, and book online in high season.
Predjama Castle: the troglodyte eagle's nest
Ten minutes from Postojna, Predjama Castle is wedged into a 123-metre cliff. Built in the 13th century, it sheltered the robber knight Erasmus, who taunted his besiegers thanks to a secret passage carved through the karst — the story comes with the audio guide, included in the ticket (€24 alone, or the €49.90 combo with Postojna). From June to September you can also visit the cave under the castle, the country's fourth-longest system.
Should you do both?
If you have a full day, yes — they don't tell the same story. They sit 40 minutes apart by road, and the order matters: Škocjan in the morning at the first tour (cool air, calm), a picnic in Divača, then Postojna and Predjama in the afternoon as the coaches start to leave. On the way, the Karst region deserves a detour: stone villages, pršut ham and terra rossa red wines. And if you sleep nearby, Piran and the coast are only 45 minutes away.
The little-known caves (often more beautiful)
Križna jama is my favourite: a rowing-boat ride across emerald underground lakes, by torchlight, with no concrete and no electricity — the cave remains exactly as the cave bears left it. The short visit takes a good hour (€13–15 by season, children €8–10), booking is essential for the long boat tours, and payment is cash only. Vilenica, near Sežana, is Europe's oldest show cave — visited since 1633 (€15, daily in August at 11 am and 3 pm). And for the curious, the modest Pekel cave near Celje hides a four-metre underground waterfall.
Planning the day
Both caves slot neatly into any west-Slovenia route — the complete travel guide shows where they fit, and our things to do in Slovenia page maps the whole region. Whatever the season, bring warm layers: the caves are the country's best rainy-day and heatwave plan.
Frequently asked questions
Which cave should I choose, Postojna or Škocjan?
Postojna with children or for a comfortable, spectacular visit (little train, giant formations). Škocjan for raw emotion: a 146 m UNESCO underground canyon with half the crowds. The two combine in one day, 40 minutes apart.
How much does Postojna Cave cost in 2026?
€34.90 for the adult ticket to the cave alone, €49.90 combined with Predjama Castle. Online booking is advisable in summer to pick your slot.
How much do the Škocjan Caves cost in 2026?
€24 per adult and €12.50 per child in July-August (slightly less off-season) for the underground canyon route. Guided departures at fixed times; arrive 30 minutes early.
Do I need to book the caves in advance?
In July-August, yes for both: Postojna sells timed slots online, and Škocjan's departures are limited. Off-season, buying on site is easy. For Križna jama, booking is essential for the long boat visits.
How cold are Slovenian caves?
A constant 10 °C at Postojna and 12 °C at Škocjan, summer and winter. Bring a fleece and closed shoes even in a heatwave — which is also what makes the caves the best visit on rainy or scorching days.
Patrick Faust
French expat in Slovenia since 2004. Founder of e-Slovénie, a Slovenia travel guide. Learn more →