Cultural heritage: What makes the cut?

German has an estimated one million properties listed as sites of historical interest. Which of them are actually worth preserving? Many were instrumentalized for torture and repression. Heritage Day on September 8 is a chance to ask which sites should be passed down to future generations. The motto this year is "Beyond the Good and Beautiful."

Monuments can slide down the unspoken "worthy of being preserved" list for various reasons, but especially when they recall dark chapters in history, like the Peenemünde Army Research Center (pictured). Nazi Germany's planned military superiority was researched here between 1936 and 1945. Forced laborers, concentration camp inmates and prisoners of war were put to work at the center.

Nazi Germany had about 70 prisoner-of-war camps, which interned hundreds of thousands of people - many of whom died in incarceration. Most of the camps have been wiped off the map and forgotten, but not in Sandbostel in Lower Saxony, where the Foundation for Remembrance maintains 22 of the original 150 POW barracks. A permanent exhibition at the site opened last spring.

The romantic Türnich Castle in North Rhine-Westphalia has a charming chapel and Baroque garden. There's only one problem: It is uninhabitable. The castle threatens to collapse as a result of earlier coal mining, which has lowered the water table and changed the ground structure. Preserving it is a major challenge.

Homeless and unemployed people were the first to live in the Schlieperblock housing development in Iserlohn in 1928. It has remained a socially troubled district ever since. Many struggle to view it as an architectural treasure. But the state conservator believes social history is also an important aspect of preserving historical sites.

Today it is difficult to imagine the suffering that took place in castle dungeons hundreds of years ago. But the Wewelsburg castle has a doubly hideous past: In the 20th century, the Nazis planned to built an ideological center there. An extra concentration camp was built nearby to house the prisoners who were to construct the center. In the end, though, the plans were not realized.

The Alte Dreherei, or Old Turning Shop, in Mülheim an der Ruhr is full of stories. It was built in 1874 as part of a railway repair shop and remained in operation until 1959. Like so many other industrial buildings in the region, it also fell into disrepair. In 2008, a preservation society restored the shop and has maintained it ever since. But is it worth saving all industrial remnants?

The Oterndorf prison mainly houses people who had slaughtered animals illegally or stolen from their neighbors. But for a prison, it wasn’t a bad place to be: warm, dry and safe with enough to eat. Once a place for petty criminals, now it's been converted into seminar rooms for management training courses. Irony aside, it's being put to use rather than simply maintained.

Since 1993, every second Sunday in September has been dedicated to historical preservation. The idea was the brainchild of former French Culture Minister Jack Lang. Heritage Day has meanwhile become an established celebration. This year, 2,700 cities and towns will open their doors to more than 8,000 sites, including the former Armenkate in Gross Pampau in Schleswig-Holstein.

The future of old building is being fiercely debated in many places. Sometimes, protesters win and buildings are saved; other times, they're torn down. The decision has to be made on a case-by-case basis. And sometimes preservation can actually move you forward - like in Naumburg, where Germany’s longest-serving street car depot has been back in operation since 2007.