Under the 
Silver Mountain

A photogrammetric survey of flooded corridors in 18th-century mountain stronghold in Lower Silesia, Poland.

About the fortress

The Silver Mountain Fortress, an imposing 18th-century mountain stronghold in Lower Silesia, Poland, stands as one of Europe’s largest and most formidable fortresses. Spanning 106 hectares, the complex encompasses a three-level bastion with 151 casemates, vast storerooms, wells, armories, a chapel, prison, hospital, bakery, brewery, workshops, and a powder magazine. Built to be self-sufficient, it housed over 3,700 soldiers and ample supplies during its peak.

SURVEYING THE FORTRESS WELLS

On May 17, 2024, a team from the Submerged Foundation embarked on a mission to document the fortress’s underwater tunnels. The stronghold features nine deep wells, legendary for their construction cost. Each of them was over 3 meters in diameter, dug to provide sufficient water supplies during sieges. Our interest in these wells stemmed from their potential historical significance and the possibility of discovering artifacts. The wells, masterpieces of pre-modern engineering, took approximately two years to complete – each. Prior archaeological projects in the Lower Silesia region, where the fortress is located, had shown that such sites could yield fascinating finds.

SURVEYING THE FORTRESS WELLS

The first dive focused on the well at the former fortress brewery. The well’s black maw, visible only with flashlights, marked the start of a challenging descent. Eight meters below the surface, we found a tunnel branching off from the well. This tunnel, known from 1980s dives, was our primary target. We inched through the tunnel, which soon transformed from roughly hewn rock to a brick-lined passage with an arched ceiling. The passage ended abruptly with a brick wall, raising numerous questions about its purpose and construction—was it for defense, water flow, or something else?

INSCRIPTIONS ON THE WALL

In Donjon’s well we encountered no additional tunnels but discovered inscriptions etched into the well walls. One clear word, “AWE,” and another less legible inscription piqued our curiosity. We meticulously 3d-scanned the fragment of the wall containing the inscription and handed it over to the historians researching the fortress’ past.

Aerial photogrammetry scan

In parallel with the dives, we collected massive UAV photoset, allowing us to come up with a detailed 3d scan of the entire stronghold and its surroundings.

A 3d scan (model) of the Silver Mountain Fortress in Lower Silesia, Poland. Created by the Submerged Foundation

THE PROCESS

The survey included both underwater and aerial photogrammetry. We scanned the details of the flooded corridors and the whole stronghold area as well.

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underwater photographs

The conditions were challenging, with silt easily stirred up, requiring us to move extremely slowly and carefully. However, our efforts paid off, resulting in a detailed photogrammetry scan of the fascinating underwater corridor extending from the wall of one of the wells.

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down the rope

Although the water level in the wells has been rising over the years, the surface is still quite deep. The divers had to descend approximately 30 meters to reach the water.

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aerial photographs

Thanks to the extensive data captured by the UAV, we were able to create a detailed 3D model of the Silver Mountain Fortress and produce an orthomosaic with a resolution of approximately 4 cm per pixel.

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wells

The stronghold features nine deep wells, legendary for their construction cost. Over 3 meters in diameter, dug to provide sufficient water supplies during sieges. Surveying those wells is the project’s main goal.

The outcomes

Creating a scan of flooded mine is one thing – but how to present it? This was one of many fields where we were learning on the go.

Outcome #1

photogrammetry scan of the flooded 
corridor ending

This tunnel, known from 1980s dives, was our primary target. We inched through the tunnel, which soon transformed from roughly hewn rock to a brick-lined passage with an arched ceiling. The passage ended abruptly with a brick wall, raising numerous questions about its purpose and construction—was it for defense, water flow, or something else?

Outcome #2

UAV Photogrammetry survey 
of the fortress

In parallel with the dives, we collected drone footage. It was used to create a detailed 3D model of the entire fortress – something that many before us had attempted, but so far without any significant results.
A scan of one of the flooded corridors in the Silver Mountain Fortress

ADDITIONAL PUBLICATIONS

Learn more about underwater photogrammetry scanning and how it helps to preserve the underwater world.

The Silver Mountain Team

The project involved underwater 3d scanning, aerial photogrammetry and ROV surveying

Divers

Marcin Stempniewicz | Submerged Foundation

Project leader, diver, photogrammetry data aquisition, photogrammetry reconstruction

Sławomir Patuła

Diver, artefacts recovery

Michał ‘Ciastek’ Gurbiel

support diver, documentalist

Aerial photogrammetry

Mateusz Zahora | Submerged Foundation

ROV Surveying

Łukasz Orlicki | Odkrywca.pl

Surface support

Michał Winek, Sylwia Sierpniowska-Saladyga, Emilia Marczewska, Waldemar Jasiński, Błażej Kabziński

Media and supporters

The project would not be possible without the support of Twierdza Srebrna Góra (Silver Mountain Fortress). We received a great deal of support from the Xdeep Exploration Support Program. You can find more about the exploration process in the monthly Odkrywca magazine.