Fortification Sv. Katarina B

A hill above the Rječina River canyon, Rijeka, Primorje-Gorski Kotar County, Croatia
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Year of build:
Original name:
Angheben II
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Military architecture
Past and Present Ownership of the Building/Site:

Public (Republika Hrvatska)

Typology and Style

The World War 2 military fortification facility, built as an underground fortification consisting of a system of a total of 12 underground tunnels and combat blocks (bunkers) just above the terrain line.
One of the few completely finished buildings in the area of the city of Rijeka was built between 1931 and 1941 ("Circular 200") and is an integral part of the steel and concrete defence belt, also known as the Vallo Alpino (translated Alpine wall). As of December 1939, the "Circular 15000" created a detailed classification of the fortifications, and according to the same, based on the known parameters, it is possible to classify the fortification of Katarina (A and B) among the large fortress ("Opera grossa") category.
The “Katarina B” stronghold consisted of two fortifications – the "Left" and the "Right" sector, respectively East and West. The two sectors are connected by corridors, which together formed one ring, and today a complete circle can be made without the need to return to the same corridor (as is the case in “Katarina A”). Given the typology of the building, fortifications of this type were built in the highest secrecy and were inaccessible to the local population. Apart from being physically inaccessible, the massive above ground structures were very skilfully camouflaged and thus almost impossible to locate.

Degree of preservation and status of protection

From a construction point of view, this is a very well-preserved fortification (the best of all those found in Rijeka), and there has even been the discovery of electrical wires still in existance (although these are assumed not to be original). Moving equipment was removed from the site. All steel domes (casemates, observatories) have remained on site. Apart from the absence of signs of moisture and a significant cracking of the structure, no dilapidated condition was found at this location nor was there a large amount of waste (probably due to the presence of different associations). The steel elements (beams and vaults) used in places where there was insufficient depth and the rocks in the upper belt (entrance parts) are corroded. Unlike Katarina A, very few of these parts can be noticed here. It is assumed that the underground concrete parts were painted after construction in the 30's, and the inscriptions on the wall (graffiti) date back to 1991. It has no cultural heritage status.

Architectural Description

The building is completed and consists of an underground part made up of a corridor (ring) system that connects combat blocks (bunkers), where their aboveground part (concrete or steel) was masterfully camouflaged. How much attention was paid to the construction itself is also evidenced by the detail of a concrete staircase with a rounded front part of the tread, which is characteristic for civil architecture. The length of the main circular tunnel connecting the fortifications of the left and right sector is about 360 metres, although taking this into account with all the corridors leading to the bunker, the total length of the tunnel is about 790 metres. Considering the size, content and number of premises, it can be assumed that "Katarina B" alongside "Katarina A" was the main fortification in the area. Just like "Katarina A", "Katarina B" had all the facilities and crew quarters necessary for longer stay in underground fortifications in the event of a siege.

"Each of the fortifications had a separate entrance and a well-equipped logistical section, with power generators for lighting, ventilation and communication. The generator room, along with the gasoline tank, was near the entrance to the "right" fortification. The “Sv. Katarina B – East” fortification had an additional bunker as well, which housed a photophone for communication between strongholds "A" and "B", and there was also a security exit, defended by the position of a light machine gun. Fire from bunkers was directed from the “Central observatory” "Osservatorio centrale", whose concrete roof was no more than 50 cm thick but was reinforced with steel and carefully camouflaged, located 14 metres above the level of the shelter.”

From: TONIĆ V., Tragom „Alpskog bedema“ u Rijeci i Hrvatskoj, Rijeka: Slobodna Država Rijeka, 2011

The underground (logistical) part of the Katarina A and Katarina B strongholds were similar, but their internal arrangement was adapted to the morphology of the hill within which the fortifications were located. According to Tonić, fortifications of the “Katarina B” stronghold had a total crew of approximately 180 officers and soldiers. It is interesting that the size and capacity of the quarters were expressed in cubic metres because the basic prerequisite for the stay of people was obviously ventilation assured by the air filters which were present in each room. The entire territory of the fortifications was surrounded by barbed wire that still exists today.

History and Historical Context

As consolidated by the Treaty of Rapallo in 1920., a border was passing through the City of Rijeka dividing the city in two parts. The western part that included Rijeka with its harbour was under the Kingdom of Italy, while the eastern part including Sušak and the river Rječina was assigned to the Kingdom of Serbs Croats and Slovenes (treaty of Rome 1924.).

The part of the frontier that was passing over the hills above Rječina river was heavily fortified by some of the main defensive corps of the so-called line “Vallo Alpino” (Alpine Wall).

“In the climate of mistrust that prevailed among European countries in the 1930s, memories of the First World War slaughters were still fresh. The battles on the Italian-Austro-Hungarian front, on the Soča River and in the Julian Alps, could be compared with the fierceness and magnitude of the tragedy of hundreds of thousands of lives lost to those in the plains of France and Belgium. After the war, there was an opinion among military strategists that it was better to invest in strong defensive lines and concrete fortifications than to count on the masses of soldiers, "cannon fodder", as a guarantee of inviolability of borders and avoiding future bloodshed.
The construction of permanent fortifications on Italy's "Eastern Frontier" began shortly after Circular no. 200 was issued: both Croatian and Slovenian papers of that time mention the digging of "huge caverns" as early as in 1931-1932.
“On April 28, 1937 (valid retroactively since December 20, 1934), a decree was issued to found a special corps of the Italian army called "Guardia alla Frontiera" (Border Guard), in order to occupy the positions situated on a line known as “Vallo Alpino” (Alpine wall). This corps was territorially divided into so-called. sectors, totalling 27, from which the first was located on the border with France on the Cote d'Azur, to the twenty-seventh, which was the city of Rijeka itself.”

The fortification was under control of military forces until 1995. However, the only period when it was used for military purpose, was in the “Battle for Rijeka”, from the mid April to beginning of May 1945. (03.05.1945. Liberation of the city of Rijeka from German occupation).


"Rapalski ugovor". Hrvatska enciklopedija digital edition (Croatian encyclopedia) (in Croatian). Miroslav Krleža Institute in Zagreb.

"Rimski sporazum". Hrvatska enciklopedija digital edition (Croatian encyclopedia) (in Croatian). Miroslav Krleža Institute in Zagreb.

TONIĆ V., Tragom „Alpskog bedema“ u Rijeci i Hrvatskoj, Rijeka: Slobodna Država Rijeka, 2011

Values of the Building

The value of this site is primarily military-historical, both locally and globally. There is much to be learned about the manner and strategy of World War II warfare. However, the architectural value of fortification should also not be underestimated. If we take into account the years when it was built, the complete secrecy that accompanied the construction, and the extremely demanding location on the slopes of the Rječina River canyon, we can safely say that from a construction point of view, this facility is an exceptional example of fortification construction of the 20th century. It is fascinating that the above ground steel domes, approximately 20-30cm thick, weighed tens of tons each. The value is certainly of an aesthetic and landscape nature as well. Namely, besides the underground itself being interesting, even more so are the above-ground bunkers, the way they camouflage and fit into the environment and the strategic positioning of them without the use of any of the sophisticated tools known today.

Description of the Urban Context and Development

Not far above the residential part of the settlement, on the slopes of Sv. Katarina, there is a Rehabilitation Centre to which traffic for vehicles is ensured and in the immediate vicinity there is a parking lot as well as entrances to the underground tunnels of Katarina B. Just before the entrances to the underground part, there are ground structures and on one of them the inscription “Credere- Obbedire – Combattere” still stands which means “Believe - Obey - Fight" as well as the "Di qui non passeranno" meaning "They shall not pass here".

New Cultural Tourist Offer Focused on Selected Building/Site

"Katarina B" is a unique location where all examples of bunkers (steel and concrete), tunnels, anti-tank positions and trenches can be seen, and which shows the Alpine Wall at its peak when there was clearly no shortage of funds or work force.

Considering that from here the view extends over the whole city and its surroundings, "tourist" parallels can be drawn, as usually happens with viewpoints. For example, one of the controlled positions was Trsat which is now a famous pilgrimage destination. It would be interesting to draw a historical parallel about the development of the city on Rječina through former strategic points, through a very accessible and well preserved story of fortification bunkers and by walking through the forest or along the already marked Rijeka promenade, a former "mulattiera", i.e. a mule track.

On the other (south) side there is a very good driveway with ground floor facilities that can serve as an info point with a place to rest and present everything that can be visited.

Education (history, geography, biodiversity), sports, recreation, entertainment, tourism - can all be incorporated here.


The archival documentation for the construction of tunnels and bunkers was not found in the State Archives, which is logical given the fact that the construction of these facilities was a very well-kept secret at the time. It is not possible to exclude the possibility of archival documentation on the Rijeka fortifications in the military archive in Rome, however, a longer period for research is needed. The documentation found was collected from private collections from various forums or archives of the Heritage Museum of Drenova.

Katarina B Approximate Floor Plan