Those people are buried in an unmarked grave pretty close to where I live.

here is a danish wiki article

The execution shed at Christianshavn (also called the shooting shed) was one of the two places where the death sentences in the Danish court battle after the occupation were consummated in 1946-50. The second place of execution was in Undallslund plantation at Viborg.

The execution shed was an architect-designed boardhouse with concrete floor built in one of the more distant parts of Holmen, at 2. Redan of Enveloppen at Margretheholm. The original drawing, which can be found in the National Archives, is referred to as "Pistol Shooting Space. Shed to Skiver" (i.e. target slices) but the place was only listed for the executions. 1]

The concrete floor with drain grate can still be seen. Enveloppen is part of Fristaden Christiania (Bådsmandsstrædes Kaserne) under the name Dyssen, and the historical powder magazine at 2. Redan is called Airconditionair conditioning. The concrete foundation lies at the end of the building's angle, right on the eastern side of the path. A wooden shed, which is based on the same drawings, but built 1980, stands by the building The cosmic flower on Syddyssen, which is the historical gunpowder magazine at 5. Redan.[[2]

30 death row inmates were executed by firing here. The most recent was Ib Birkedal Hansen on 20 July 1950 at 9pm. 01:00, which was also the last to be executed in Denmark. 16 others were executed in Undallslund.[ 3] [[4]