Warsaw Uprising Museum
The historical building of the tram power plant houses a modern exhibition about the destruction of the Warsaw in 1944. The museum doesn't require any additional assistance from guides as the museum sufficiently tells the tragic story. In 1944, during the Uprising, German Nazis murdered around 200 000 people, mostly civillians and destroy the heritage of 25 generations of Varsovians. This is one of the least known and most tragic events of the 2nd World War.
Pro tip: the exhibition is vast and very rich. Therefore it is very easy to miss whole chunks of the story. Make sure you find your way to level -1: on both sides of the great big screen int he main hall, there are entrances to the level below, where there are reconstructed sewers, like the ones that had to be used by Varsovians trying to escape the massacre. Also, don't miss the film "City of Ruins", in the small cinema in the main hall. There might be a queue to see it, but it is totally worth it.