Reserve powder magazine

Poland revolted in 1863 (it was a part of Russian Empire in 19 AC). The tsarist government brutally suppressed the uprising, but it, however, caused an heating of the politic situation in Europe. The invade of British fleet in the Baltic was expected. The crisis initiated the modernization of Russian coastal defenses, and in 1864 a large-scale construction was launched at the Trongsund position.
The picture shows a large so called reserve powder magazine on the north side of the redoubt next to the pear.