The tunnel entrance of the underground Željava air base carved into Mount Plješevica, Croatia

Abandoned Military Complex

Objekat 505 — the Underground Base

Željava Air Base · Lika & Plitvice

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CATEGORY: Abandoned Military Complex
COUNTRY: Croatia
REGION: Željava Air Base · Lika & Plitvice
DURATION: Half a day

ABOUT THIS ATTRACTION

Objekat 505 is the heart of Željava: a network of tunnel galleries cut deep into Mount Plješevica, designed to shelter, arm and launch an entire fighter wing from inside the mountain. Four tunnel exits opened onto the taxiways; inside were hangars, workshops, fuel stores and crew spaces, connected by underground roads. Above ground sits the full-length runway and taxiway system, its asphalt now torn open by the demolition charges of 1992. Walking the site today, you move between the scale of the engineering — the galleries are enormous — and the eerie quiet of a place built for a war that never came, destroyed by one that did.

HISTORY & BACKGROUND

The story behind it

Construction began in 1948, inspired by the Swedish Göta Wing mountain hangars, and was completed in 1968 — twenty years of secret work on one of the most expensive military projects in postwar Europe, costing SFRY around 6 billion of today’s dollars. The base housed the 117th Fighter Aviation Regiment with MiG-21s. In 1991, during the breakup of Yugoslavia, the Yugoslav People’s Army blew the runway with pre-built demolition chambers as it withdrew, and in 1992 the Army of Serbian Krajina finished the destruction with an additional 56 tonnes of explosives — the detonation shook Bihać, and locals reported smoke rising from the tunnels for six months.

WHAT TO SEE

What to see here

The tunnel mouths cut into Mount Plješevica — walkable up to the safety barriers.

The cratered runway and taxiways above ground, walkable on foot.

The derelict Dakota C-47 standing at the entrance.

The mountain-top radar station plateau above, with views over the Una valley.

GOOD TO KNOW

Facts & Curiosities

Objekat 505 was the largest underground air base in SFRY and one of the largest in Europe — built 1948–1968 at a cost of around 6 billion of today’s dollars.

The base could shelter and service an entire fighter wing inside the mountain; four tunnel exits opened onto the taxiways.

In 1991–1992 the base was destroyed with demolition charges, including 56 tonnes of additional explosives in 1992 — the blast shook nearby Bihać.

The complex straddles the Croatia–Bosnia border: parts lie in Lika-Senj County (Croatia) and parts in the Bihać area (Bosnia and Herzegovina).

WHY IT MATTERS

Why it matters

Željava is the most impressive abandoned military site in the Balkans — a Cold War megastructure you can walk through freely. For a visitor it is the unexpected, unforgettable stop between Plitvice and Bihać.

PRACTICAL INFORMATION

Before you go

Access

The site is reached from the village of Željava (Općina Plitvička Jezera) on the Croatian side, or from Bihać on the Bosnian side. The border crossing at the site is closed; do not cross the boundary line on the runway — the border runs through it.

Best Time

April to October, in dry weather. Wear sturdy shoes; tunnels beyond the barriers are dangerous and unofficial guides are recommended.

Pairing

Combine with Plitvice (20 minutes), Rastoke at Slunj, or Bihać and the Una valley across the border.

THROUGH THE LENS