Just on the outskirts of Mlawa, on 17 January 1945, the Gestapo murdered 364 Polish resistance fighters, political prisoners and Soviet prisoners of war.

Current status: Monument (2012).

Location: 53°06'12.81"N 20°21'41.37"E

Get there: Car.

My comment:

A mausoleum has been established for the victims on the site.

Follow up in books:  Lukas, Richard C: Forgotten Holocaust: The Poles Under German Occupation 1939-1944 (2008).