It was only the construction of the railway, which was carried out in the years 1871-1873, that forced large changes in the surrounding area, and above all the execution of a huge embankment. A high causeway was built across the lake, and there was a tunnel going through it, that’s also where the canal was made. The canal was built by French prisoners after losing France in the war with Prussia (1870-1871). Today it is called The Warminski Channel allowing to swim from Lake Szeląg Mały to Lake Szeląg Wielki. It is the only navigation tunnel in Poland.