A museum charting the history of National Socialism in Germany has launched an open design contest for its £14m ($23.5m, €17m) expansion project.

The Obersalzberg Centre of Documentation in Berchtesgaden, Germany is located close to Adolf Hitler’s now-demolished Kehlsteinhaus – or Eagle’s Nest – mountain retreat.

The museum opened in 1999 and attracts 160,000 visitors per year. The expansion project will refurbish the existing 675sq m (7,266sq ft) building and create a new 2,500sq m (26,910sq ft) combined visitor centre, exhibition space and education centre.

As part of the design contest, ideas on how to overhaul the museum’s surrounding landscape are being sought.

The winner of the contest will be awarded £36,000 ($60,421, €43,659), with prizes also available for second to fourth place finishers, as well as for four honourable mentions.

Kehlsteinhaus became a second seat of government for Nazi Germany in 1933. Intended as a 50th birthday present for Hitler, the actual number of times he visited the facility is still debated.

The deadline for submissions to the design contest is 30 May, 2014.