The Słupia, the Radunia, and the Wierzyca are rivers whose location and energy of water flow was taken advantage of to build hydroelectric power plants. Many of them are still operating and can be visited. The oldest such power plant in Europe, Struga, or the Radunia’s highest-situated plant in Bielkowo, are only a few of the facilities well worth seeing. The principles of physics, chemistry, and mathematics are contained in machines and post-industrial sites, and presented at thematic exhibitions, such as in the Hewelianum Centre.
The municipal water-pipe system in Prabuty
The monumental water-pipe system from the 18th Century was built because the town fell victim to many fires. The tunnels of the water-pipe system go under the Old Town in Prabuty.
Most of the architecture of the town at that time was wooden and most of the buildings had thatched roofs. The water-pipe system ran in archway tunnels under the market. They consisted of a network of wooden and cast-iron pipes, which carried the water to the well in the market. They are located 3.5 m below the surface. They were constructed using the open-pit method. The entrance is located in the foundations of the old town walls on the east side. They are shaped like an inverted capital letter "F". The walls of the tunnels are made of red brick, are 70-80 cm thick and have a barrel vaulting. The height of the tunnels varies from 170 to 230 cm and the width from 120 to 130 cm. The length of the tunnel is 120 m and the east and west branch tunnels are 45 and 42 m in length respectively. Each branch begins and ends with a container, which can be viewed through special openings. After the construction of the water-pipe system, each container had a well on top of it, which was replaced in the 19th Century by pumps. The diameter of each of the containers is approximately 4 m and the height from the floor to street level is over 5 m. In the tunnels you can see old hooks and cavities for lamps and torches. It is one of the few monuments of Prussian engineering in this area. After exiting the water-pipe system there is a view of the architecture of the old municipal sugar mill, built in 1833. The neighbouring meadows mark the location of the second lake surrounding the town (Lake Młyńskie). The water-pipe system was built with significant subsidies from the Prussian King Frederick William I, who gave 10 000 thalers for this cause.