24 May 2013

Tunnel under the Danube between Nagymaros and Visegrád

There are many legends in the Hungarian folklore about tunnels under the Danube. Where once a Roman watchtower, a medieval castle, or any kind of bigger ruin stood on the banks of the Danube we can be sure that the locals have the knowledge about a mysterious tunnel leadning to the other side. Most of these tales are just fantasies, in any era it was much cheaper to row, than to dig. I know about only one tunnel under the Danube that exists. And fortunately its owner, The Danube Regional Waterworks Co. opens this tunnel for the public once a year. After short organizing twenty-three of us started our 550 meter (600 yards) journey. 

It is always a great experience to cross the Danube on dry feet. Between Visegrád and Nagymaros this opportunity existed only once, when Emperor Franz Joseph personally lead a combat training exercise, which had a part to construct a pontoon bridge across the river.

We choose the Visegrád departure, so we had the chance to visit some Roman ruins on the right bank (unfortunately we found no tunnels in them). Somewhat south from the town’s soccer field starts a solid road, which lead us into the former construction grounds of the Nagymaros-Gabcíkovo hydroelectric power-plant. Once they planned the sluice gates in this small man-made bay. These two bays will become parts of the land by upsilting, as they were before the construction.
The utility tunnel is runnig right there where the power-plant dam was planned. The tunnel entrance is situated exactly at river kilometer 1696, and is marked by blue iron plates. In 1992-1993 it became clear for everyone, that this dam would never be completed. But the designers thought it would be good if some kind of connection is built between the two sides. This utility tunnel, built by Mélyépterv Zrt. Was installed in 1995. Not only electric cables and water pipes were installed in the tunnel, but there is also a possibility for gaining daily 3000 cubic meters of fresh water through drain pipes built in the gravel. You may imagine a leaky pipe under the Danube bed and over the tunnel, where pebbles are filtering all mud from the fresh water. But alas, this is not working yet, however it is already built.
Entering the blue steel entrance, we took a few steps down the stairway into a receptive room, where we found a small exhibition between the taps, pipes and switchboards. This exhibition has two different topics, on one hand it gives us information on the local nature, flora and fauna. On the other hand it discusses the main topic: the abandoned construction of the Nagymaros dam (with a very hard-to-read Hungarian blue cursive writing). Those who had no patience (and time) to read all the information were compensated by the old photographs on the unrecognizable defaced landscape. After listening our guide’s introduction (which he possibly told at least two dozen times that day) the tall ones took their safety helmets and we could begun our journey under the Danube. 

Cables and pipes guided us not only on both sides, but over us as well. There were electric cables, internet cables, and wires of automatic control systems. On the right side below ran a sewer, on the left two fresh water pipes, out of them only one operated. The tunnel, made of concrete rings has a diameter of 3 meters and runs 17 meters under the surface. Its track was exploded into the volcanic stones of the riverbed. Over it there is 4 meters of Danubian gravel and the height of the river itself depending on the current water level. 
Due to water pressure in some places the infiltrating water forms small concrete dripstones or stalactites. To avoid this phenomenon they inject greasy material (oblique bars above). Despite all efforts still small water drops are twinkling at the ends of the concrete stalactites. After dropping, they form stalagmites on the tunnel floor. This is quite an insignificant water infiltration, the tunnel is prepared for more serious malfunctions.
The 550 meters long utility tunnel is divided into sections by lock doors. For example in case of fire not all of the system gets damaged, but the damage may be somewhat localized. But these lock doors could not stand against a serious water break-in. That’s why the entrance was built over the high water mark. On our way we thought if this tunnel would be open all year the ferryman of Nagymaros and Visegrád would lost a lot of money. It is quite easy to pass even with a bike. 
In an average pace this trip would take 5 minutes, unless we weren’t so curious. Fortunately our guide gave us many interesting information on the tunnel, on the failed dam construction, and the utilities crossing the river. This way we spent more than a quarter hour under the Danube. At the exit, there was another small exhibition, but we haven’t stayed long. On the ground we enjoyed the same nice welcome just like on the Visegrád side. The frostbitten visitors received sandwiches and tea in the waterworks tents. We also received several free gifts, like cell phone case, beermat, pecilbox, stickers. Finally we signed the guest book: we all enjoyed the trip very much! 

I would like to say thank you to to the Danube Regional Waterworks for organizing this trip, and for all employees who held out in such windy weather. The facility is open each year, could be visited in organized groups. More information on the webpage: dmrvzrt.hu


  1. This looks amazing! How did you find out about this tour? Visegrad is one of my favorite places to visit and I would love to do this tour! I tried the website provided but it's difficult to find any information even with Google translate. Great post!

  2. Hi, this trip is quite occasional, last trip was on 2017 april http://www.dmrvrt.hu/hu/alagut1, and in october 2016, according to this Hungarian website: http://www.dmrvrt.hu/hu/kozmu_alagut_2015_idop Looks like, they used my photo. :)