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The most expensive project of the former country: air base with an underground facility in Lika

We visited Zeljava, a former air military base known for its underground facility codenamed Facility 505, at the bottom of Pljesivica mountain, on the border between Croatia and Bosnia and Herzegovina.

One of the entrance to the "Klek" object

Considering the time when this military base was built, its size, the amount of material used, the facility is without exaggeration among the impressive ones. Today, Željava is completely neglected and quite dangerous, but because of it, now is the target of many enthusiasts who love military and war history, aviation and abandoned facilities.

Why there?

The position of the building was chosen after extensive studies, with the greatest attention being paid to its geostrategic significance. The basic requirement was that it must be located on the then state geostrategic base: deep enough in the state territory to be able to defend itself long and successfully, and evenly spaced from the most important strategic goals and facilities. Estimates also required that the new facility must be able to withstand the impact of a 20-kiloton bomb in the first crash, and construction was modeled on similar facilities in Sweden. When choosing the location, the creators and designers were helped by the fact that there were several favorably located mountains in such a designed belt, so the choice fell on Plješevica. Its geomorphological composition was ideal for this type of building, which, in turn, set the builders very difficult tasks and field work.

The mountain itself was an ideal obstacle to any sudden attack, very close is Velebit mountain, then the Adriatic Sea, while on the other side is the Slavonian plain, which prevented potential enemies from suddenly approaching the building.

The facility was built to serve for the next few decades without major alterations. Taking into account the correctly assessed geostrategic characteristics, a very favorable logistics base, the proximity of auxiliary airports, facilities and other resources, it can be said that the military significance of the facility was enormous.

When did it all start?

The design, that is, the elaboration of the basic idea, became concrete in 1954, after the decision of the political and military leadership. A year later, the Air Force Command formed a commission that, analyzing a number of conditions, proposed the development of a program and project documentation. The original plan was not so grandiose, but the main project was then expanded to the size in which the facility was later realized. Construction was conditioned by the composition of the land, with a favorable morphological picture - natural bays for entrances and ridges that separate them. The airport was built until 1968, when it was put into operation due to the crisis in the then Czechoslovakia. During the following years, it was constantly refined and equipped with new equipment, and it was built for a full 12 years.

What did the object in the womb of Plješivica look like?

The tactical-technical features were impressive: the three galleries to accommodate the 58 aircraft were interconnected in an M-shape with an elongated middle arm. The gallery profile was built according to the dimensions of the aircraft owned by Klek (MiG 21). There were, among others, warehouses for rockets and bombs, fuel tanks, power generators, air conditioning chambers, kitchens, classrooms, ambulances. The outer part of the building - the airport, consisted of five runways (two runways and three runways).

Object sheme, photo:

The base was supplied with kerosene by its own pipeline from a military warehouse near Bihać. The aircraft were deployed inside the facility by electric accumulator tractors. Each parking space had its own connection to refuel the aircraft. Living and working conditions are provided for the intended use of the facility with full autonomy of up to 30 days.

Gallery: Željava in history (source: wikipedia)

Heavy reinforced concrete doors, which separated the galleries from external influences, were housed in separate niches on the gallery side and had built-in anti-shock valves. They were closed manually or electrically, in one gallery and hydraulically. The climatic conditions in the building itself were ideal.

End of operation of the air base

When the military-political and security situation in the former state deteriorated so much that it was obvious that the airport would find itself in a hopeless environment, a decision was made to destroy it. That is what happened on May 16, 1992. year at 5 and 30 o'clock in the morning with over 50 tons of explosives. Runways are mined at intervals of 50 to 100 meters. Most of the personnel who had been operating in the base until then were transported by B707, B727 and DC-9 aircraft a few days before the complete destruction of this base.

At the beginning of the Homeland War, the enemy army operated from this airport several times. In September 1991, MIG21 took off from Željava and rocketed a TV transmitter on Sljeme, and on October 7 of the same year, Banski Dvori was rocketed. Croatian soldiers who found themselves at the beginning of the war on Željava managed to secure MIGs for the Croatian Army. Namely, on February 4, 1992, Colonel Danijel Borović flew from Željava to Pula, thus making the first supersonic fighter aircraft available to the HV. Two other Croatian pilots, Ivan Selak and Ivica Ivandić, flew over Croatia, while Rudolf Perešin landed the MIG-21 in Klagenfurt.

Željava today

By bombing the airport facilities and runways, the airport was completely put out of use. The degree of damage varies by object. The external buildings were completely destroyed, and the remains were visibly healed under the influence of nature. Although detonation sites can be seen in many places, the Klek underground facility was not demolished by blasting and is completely passable. Most of the devastation has followed in recent years, as the facility has been targeted by collectors of secondary raw materials. As there was a dividing line in the immediate vicinity of the airport during the aggression against Croatia, the entire area of ​​the airport was mined. The HV declared the airport and the entire facility unpromising, and in accordance with the border agreements according to which military units are not allowed to reside in the area of ​​15 km from the state border, it left the airport itself.

Gallery: Željava today

The tunnels of the Klek facility (the underground part of the Željava airport) were severely damaged by the aggressor who mined it in 1992, some parts of the tunnel are in very poor condition, so they are in danger of collapsing. The entire facility is contaminated with PCBs and dangerous to health, and ionization smoke detectors, numbering in the hundreds of tunnel ceilings, lurk with radioactive americium-241 content that is easily absorbed in the lungs and can cause cancer and genetic damage in extreme cases. The destruction of the airport also caused great environmental damage, and a high concentration of chemical compounds, polychlorinated biphenyls (PCBs), was discovered, especially in tunnel 1.


If you decide to visit the Klek building, be very careful because in certain places inside the building there are large pieces of concrete hanging from the ceiling, while in other places there is a risk of collapse of the tunnels.

Protect your respiratory organs as air pollution in underground facilities has been proven.

NEVER leave concreted and asphalted areas around the building, the area is extremely contaminated with mines (literally a meter from concrete / asphalt) and demining of that area by HCR is currently underway.

If you find yourself in the area of ​​a former base, you will most likely come across the police, who are here to warn you of the dangers that we have mentioned, but their main task is to guard the border since it is the established route of illegal border crossings between BiH and Croatia. For this reason, the forest (visible above in the gallery) was cleared along the mountain in order to make it easier to monitor the border itself.

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