|Open:||no restriction, tunnel entered on guided tours, after appointment |
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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|1469||Graf Dietrich III. von Manderscheid-Blankenheim inherited Blankenstein and built a new water supply.|
|1999-2000||restoration of the whole water supply.|
Close to the castle of Blankenstein is a 15m high rock, called Tiergarten. The Tiergarten Tunnel is going through this rock. It was built by Graf Dietrich III. von Manderscheid-Blankenheim, who inherited Blankenstein in 1469. He immediately built a new water supply for the castle, by constructing a wooden pipe from a spring about one kilometre from the castle.
The problems of the water conduit were a valley and the rock. The Romans would have built a channel, an aquaeduct and a tunnel, all with a constant gradient. Technology in the Middle Ages knew about pressure lines, so the valley was crossed with a pressure line. A big problem was the rock. North of the alps, tunnels from the time between 5th and 15th century are really rare. Tunnels are very complicated and both, technology and sufficient labour force is needed.
The technique which was used for this tunnel is very old, as it reduces the difficulties. The tunnel was built in small pieces, after vertical shafts were constructed. The 150m long tunnel is a sequence of six short pieces, up to 30m long. The possible error in direction was only a sixth, and it was possible to determine the direction by sounds from the shaft. This method is called Qanat.
The whole ensemble is restored and my be visited. This includes the spring, the former pressure line, the channel to the tunnel, the tunnel, and finally the cistern were the water was kept. The pressure line is now defunct, but its location is still visible. It is possible to walk a short piece into the tunnel, but only from the southern end. The tunnel is closed by a gate, so it is possible to have a look into the tunnel all the time, but entering the tunnel is possible only with guided tours.