The US Holocaust Memorial Museum has returned a set of historic wooden barracks to Auschwitz.

The barracks, which were originally used to cram Nazi prisoners in for sleep by the dozens, were on loan from the Auschwitz museum for 24 years.

The US museum finally sent back the barracks—half a wooden building—which arrived in Poland Sunday.

The barracks will now go through a conservation process before being reinstated at the Auschwitz site.

The Holocaust Memorial Museum was originally granted the loan in 1989, and the agreement was extended in 1999 for 10 more years. In 2003, however, Poland passed a law prohibiting the loan of Polish historical artifacts for more than five years.

The barracks have been a centerpiece of the US site since its opening, and the Holocaust Memorial Museum negotiated for years to try and keep the set.

Now, the exhibit will be replaced by a set of barracks from Birkenau, which the museum will permanently own.