Željava Air Base: The Secret Military Base Hidden in the Mountain

On the border between Croatia and Bosnia and Herzegovina, right next to the Bosnian town of Bihać, lies one of the most unusual places in the Balkans: Željava Air Base. Built in 1968, it was once the largest and most expensive underground air base in Yugoslavia, designed to withstand even nuclear attacks.

Imagine a real underground military city hidden inside a mountain, with tunnels, hangars, and miles of passageways — all built to keep aircraft and military staff safe from enemy eyes.

Today, the base is abandoned and open, making it a fascinating spot for adventure seekers, bikers, photographers, or anyone curious about forgotten Cold War relics.

Exploring Željava Air Base feels like stepping onto a post-apocalyptic movie set. The massive tunnels that once housed fighter jets are still there: dark, damp, and covered with graffiti. It’s a unique mix of history, mystery, and adrenaline.

For photography lovers, this place is a goldmine of dramatic angles, especially with motorcycles or cars on the old runways. For the simply curious, like us, it was an extraordinary chance to walk inside a space that was secret and off-limits for decades.

• The base could host around 120 fighter jets, completely hidden inside the mountain.
• It had its own power, ventilation, and communication systems — fully independent.
• Construction cost the equivalent of 6 billion USD in today’s money.
• During the wars of the 1990s, it was intentionally destroyed by the Yugoslav army to prevent enemies from using it.
• The destruction is still visible today: blown-up runways and damaged tunnels.
• At the entrance stands an old fighter jet, adding to the eerie atmosphere.
• One of the runways even crosses the actual Croatia–Bosnia border

Željava Air Base sits just a few milles from Bihać (Bosnia) and close to the Croatian entrance of Plitvice Lakes National Park, one of Croatia’s top attractions.

We were staying in a nearby village near Plitvice, and with some free time, the accommodation staff suggested this site — which is usually not on typical tourist itineraries.

The main entrance is in Croatia, but some runways and tunnels stretch into Bosnian territory.

At the site, you’ll find:

• Motorcyclists and adventurers, often using the runways freely

• An old abandoned plane at the entrance

• A small café nearby

We entered one of the easier-access tunnels but, due to the complete darkness inside, we turned back and instead explored the gigantic runway. Without noticing, we had actually crossed into Bosnia and saw some police border facilities.

⚠️ Important: Some areas may still have landmine risks. Stick to well-used paths, don’t wander into the forests or grassy areas, and follow where others clearly go.

If you’re planning to visit Željava, combine it with other highlights in the area:

• Slunj (Croatia) — a charming small town with a waterfall and public park.
• Plitvice Lakes National Park (Croatia) — just 20 minutes away, famous for its turquoise lakes and waterfalls.
• Bihać (Bosnia) — a pleasant town with local restaurants and affordable prices. Remember: Bosnia is outside the EU and Schengen zone.

• Bring a flashlight (your phone won’t be enough inside the tunnels).
• Wear good shoes — the area is damp and rugged.
• Visit on a dry day for better conditions.
• Go with a sense of adventure — it’s an abandoned site, not a tourist attraction.

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