July 25th: Tour of Kaliningrad City
On the next day after the flight, July 25th, I visited museums in the city of Kaliningrad. I first went to the World Ocean Museum, where there were various ships (including research ships, submarines, seaplanes, etc.) and aquariums. I visited the research ship and the submarine, but the explanations were all Russian that I could not understand.
In the evening, I visited the birthplace of the map theory, the fishing village of Kaliningrad. The famous Königsberg Seven Bridge problem happened here. In 1735, Leonhard Euler proposed that there was no way to walk seven bridges in a one-off manner without repeating it, and published a paper in the following year. After the communist bombing of the Second World War, there were only five of the original seven bridges, which could be passed in one go, so I walked five bridges.