Don’t let the sailors tell you you have to cross oceans to circumnavigate the globe! Just walking around the headwaters of the Pregolya River is equivalent.

While this would have worked in Euler’s time, the puzzle in fact became unsolvable around 1873 when canals were built in the Masurian lakes effectively connecting a tributary of the Pregolya with a tributary of the Vistulato the south and cutting of this route. Maybe hopping across lock gates when they’re closed doesn’t count as a bridge tho?