It has been a tumultuous year for one prominent German property developer: his efforts to sell his penthouse atop a Nazi-era air raid shelter have stalled, and just weeks ago his firm filed for insolvency.

The one-two punch for the developer, Stefan Hoeglmaier, and his company, Euroboden, mirror the travails of the broader property sector across Europe's largest economy as it suffers its worst slump in decades.

For years, low interest rates fueled a global boom, igniting interest in German property, seen as safe and stable as the country.