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 historic Water Forge in Oliwa

It is the former Mill XIII, once the largest industrial establishment by the Oliwa Stream, and part of an enormous estate. Currently it is the only monument of its kind to be found in northern Poland.

The forge, by virtue of its two large hammers called a "hammer forge", is mentioned in written sources as early as in 1597, when it was the property of a great landowner, Jan Klinghammer, who later sold it to the Abbot of the Oliwa Cistercians, Dawid Konarski.

Two iron forges operated here at that time - the large forge, which currently houses a museum, and the small one, as well as a gunpowder mill. The water network was different back then, as was the development in the vicinity of the great forge. The latter yielded huge profits to the monastery. In the 18th Century, the leaseholder of the establishment paid 140 florins a year and provided iron to the monastery in the amount of 3.5 ship pounds (1 ship pound = 139 kg). The production of the forge in 1830 was 1340 ship pounds.

The establishment remained intact after the military operations of 1945 and was taken over by the "Żeliwiak" cooperative, which, after operating it for two years, abandoned the plant due to production unprofitability. Northern Poland's only industrial establishment of its kind was gradually falling into disrepair.

Following interventions by historic buildings enthusiasts, in 1957 the ownership of the mill was transferred to the NOT Museum of Technology in Warsaw. After securing the ruined building and its appliances, and finding its documentation and technical plans, the renovated facility was turned into a museum, which opened on 17 June 1978.

The Water Forge admits individual tourists and groups. Production was not resumed - the operation of the plant is only demonstrated and metal souvenirs for visitors are produced. The Forge's devices, typically for the Renaissance, consist of three water wheels, two massive oaken shafts, hammers, furnace, large cutters for iron.

Next to the mill, two locks, a dam, and a "large forge pond" have survived in their original form. Mill XIII also featured two independent workshops by the stream, connected with a wide roof. A little further along stands the recently-renovated storyed manor from the late 18th Century (later rebuilt), which belonged to the owner of Mill XV.