Located roughly 5 kilometer south-west of the Thekenberge is the sandstone formation of the Regenstein. Fortified since mediaeval times the old fortress of Regenstein still guards the top of the sandstone rock formation and the nearby town of Blankenburg.

In the eastern part of the Regenstein construction work had began on another underground facility. The Regenstein formation had much steeper cliffs than the Thekenberge. Geological assessments showed that the sandstone here was from a much superior quality than at the Thekenberge.? It this superior quality of the sandstone who made the Regenstein much more suitable for the erection of an underground facility. Many natural caves and tunnels forming part of the fortress of Regenstein were located in the western part of the Regenstein.

Allied reconnaissance soon made out some newly constructed military buildings in area of the medieval fortress, but they were nor sure what exactly was going on the ground. The newly constructed buildings housed the headquarters of the Organization Todt. Design-drawings were soon made up. One of the first was dated August 14, 1944. This design was not adopted. The final design was drawn up in October, 1944. It was the design used in the construction work.

The design work was undertaken by the construction office of the Organization Todt in Berlin. Dr. Rolle was the engineer in charge and the geologist of the facility. Together with the Organization Todt Dr. Rolle was to draw up the design. His ideas and recommendations were not used by the Organization Todt. The Todt design incorporated a minimal rock cover of 25 m. After the construction work had begun? the decision was taken to change the angle of directions for the tunnels.???

Obersteiger Gartner and Dr. Rolle the geologist of the project were in charge of the construction. As tenant company Schaeffer & Bodenberg was to move in. The company located in the close-by city of Magdeburg produced special measuring instruments. Just bombed-out the company received the space in the new facility. The facility received the code-name Odawerk.

The company of Schaefer & Bodenberg signed sub-contracts with 18 other companies who were employed in the construction work. All payments were undertaken by the Industriekontor. With 150 workers on hand the Brandt company begun work on the first tunnel in June of 1944. Already in August the experienced company Gross-Deutsche Schachtbau GmbH took over the further construction work. The company employed German miners who were on loan from the German Army. Besides the German miners and trades people, Ukrainian, Polish and Italian workers were employed. Over 60 miners, 260 German and 290 foreign workers were employed to complete the project.? The Brandt company was involved in the construction work outside of the facility. A further 15 specialized companies were involved in the project. No concentration camp inmates were employed here. In contrast to the Malachit project were the ventilation shafts went straight up, here in the project Turmalin the shafts went up in an angle. The shafts had a diameter of 90 cm.

The main difference between the two designs was a change in the lay-out of the production tunnels. In the adopted design the tunnels were constructed in a 14-degree angle. Without question the changing of the tunnel angle came as a result of the geological assessments. The design of October 1944 showed an area of 68,000 square meter, of this space 55,000 square meter could be used for industrial use. All production tunnels were 8 meters wide. Of the planned 53 tunnels, 29 of them had a length of 52 meter. The other 23 tunnels had different lengths. These tunnels were located on the south and north side of the main driving tunnel which run in a? northwesterly to southeasterly direction. This tunnel was the main tunnel of the facility. The side entrances C,? D, and E were located on the north side of the facility. A separate group of repair shops and a paint-shop could be reached through side entrance B.? The thickness of the rock cover over the facility ranged from 21 to 70 m.

At the end of the war a space of 18,000 square meter or 26% of the facility was finished. The two long mechanical shops on the southern site of the entrance housed tool-machinery for the production of small parts. The 7 shorter tunnels located to the north of the main driving tunnel between entrance A and C housed the spray-painting shop, tool storage room and a machine shop. A black-smith shop and a repair shop were housed in the 3 short tunnels located near the entrance on the northern side of the driving tunnel.

The mining work was undertaken by the Gross-Deutsche Schachtbau GmbH. The company used the short tunnel near entrance D as storage area. All other tunnels had no special floors installed yet and were partly not even finished to full-size. The smallest of the driving tunnels was 3 m high and 3 m wide. Production and driving tunnels had vertical sidewalls and rounded ceilings. They were 8 m wide and 6 m high. All the smaller traverse tunnels were 6 m wide and 4.5 m high. The workshops on the southern side near entrance A were supported by U-shaped steel girders lined with concrete blocks. Only partly lined was the close-by repair-shop. The traverse tunnel were the third repair-shop was located, was only lined for a short distance. In the rest of the tunnel the sandstone was shaped in the shape of the used lining. The finishing of the tunnels in such a way was only undertaken in the projects of the Anhydrite Program. A similar finish was used at the main driving tunnel. Were the rock formation was bridle the tunnels were lined and supported.

Except for one tunnel all tunnels were constructed with normal mining methods. With the help of jack-hammers a number of blasting holes were drilled into the rock. Dynamite was placed into the holes and the dynamite set off. Dredgers took the blasted rock to field-lorries which transported the spoil out.

At first a tunnel 4 m wide and 3 m high was driven into the rock. Then the tunnel was finished to size, starting with the ceiling which was extended to its full size and then the rest of the tunnel was finished. This technique allowed to install the ceiling supports if needed without creating a problem. The only tunnel constructed differently was the main driving tunnel. Here a tunnel boring machine was used. It drilled a hole 3-m in diameter into the rock. This method could be only used in fairly soft rock. At the end of the war the tunnel boring machine was found by the Americans. Such a machine was only found here in the Regenstein. The machine was made up of three sections. The first section was the chassis. A rotating drum with teeth was mounted in the front. The drum with a diameter of 3 m took out the rock, dropped it onto a conveyor-belt and transported the rock to the back. Under the cutting drum two rotating knives were located. The knives shaped the flat bottom of the tunnel.

The second section of the machine was made up of an hydraulic arm that advanced the cutting drum forward. Side arms on that section held the machine in place so that it could not move back. The third section housed a diesel engine and all controls of the machine. The conveyor belt transported the rock back running under the two last sections of the machine to a second conveyor belt which loaded the rock into field lorries. All three sections were equipped with wheels so that the machine could be moved forwards or backwards.

A temporary ventilation system was installed which was to be exchanged for a permanent system. Transformer stations outside entrances A and E supplied the needed electricity. No special steps were taken to camouflage the facility. Entrance A received a support and was lined. Before the Americans reached the facility entrances B, C and D were blown up. Steam was supplied from a building located just out-side of entrance A. The workers were housed in a camp close-by.

Without question the always mentioned design bureau for sub-marines could have been housed in the restaurant of the fortress of Regenstein. It is very questionable that the design bureau had anything to do with the Project Termalin. It is known that the production planning for the Type XXI sub-marine was undertaken at the Gl?ckauf (IBG) plant in Blankenburg between July and December of 1943.

After the war the history of the facility is very similar to the history of the Thekenberg facility. The Americans moved out and shortly after the Russians took over. In the 80's the complex was re-constructed for use by the NVA. The old Turmalin complex was the most expensive facility of the different NVA underground projects.

In contrast to the NVA depot in the Thekenberge the Regenstein facility could be hermetically sealed off in a case of a nuclear strike by NATO. All ventilation shafts could be sealed from the central control room. A well, 70 m deep, could in an emergency supply the water. If the energy supply from the nearby town of Blankenburg would be disrupted installed diesel generators would take over. A loading ramp 600 meters long made a quick loading and un-loading possible. All of the NVA complex depots stored provisions, equipment and ammunition for the forward troops of the NVA.

?After the unification the Bundeswehr took over the complex and the facility it was used to store medical supplies.