The Siegfried Line, the 630-kilometer network of bunkers Hitler built in a vain attempt to protect his western frontier from an Allied invasion, is finally serving a purpose six decades after the end of World War II -- as a quiet haven for wild cats, bats and a host of other rare species.
After the war the Allies blew up most of the more than 18,000 bunkers that made up what the Germans call the "Westwall." Since then, nature has conquered the ruins which now lie overgrown in the fields and forests of western Germany stretching from the Dutch border to Switzerland.
This relic of the Nazi era was ignored by successive German governments until the 1960s and 1970s when regional authorities began ordering the removal of the concrete remains to make way for construction or farming, and to avoid compensation claims from walkers injured while climbing into them.
But wildlife groups have been battling to stop the bulldozers and have had some success, buying individual bunkers, reaching deals with local councils and getting regional authorities to halt the dismantling, at least temporarily.
"The bunkers have developed into wildlife islands over the last 60 years, they're a haven for animals," Sebastian Schöne, a wildlife expert for BUND, the German section of Friends of the Earth International, told SPIEGEL ONLINE.
"Wildcats move into them in May to have their young and they shelter there in the winter, as do field mice, which is convenient for the cats. The wildlife also attracts birds of prey."
Rare Bats Snooze in Machine Gun Nests
At least 10 types of bats -- strictly protected under international wildlife regulations -- have moved into many of the bunkers, including the rare mouse-eared bat and pond bat.
"The bats hide deep in cracks in the concrete all year round, it's an excellent place for them," said Markus Thies, an expert on bats at the German wildlife organization NABU who has been lobbying to save the Westwall for 20 years.
"They're hard to spot," said Thies, who heads a team of 10 enthusiasts who spend their free time scouring bunkers for bats and fencing them off to stop hikers from disturbing them in the Eifel hills of western Germany.
Foxes trot nonchalantly along the anti-tank trenches, martens and badgers snooze comfortably amid meter-thick concrete walls that once housed watchful Wehrmacht soldiers manning machine gun nests and anti-aircraft batteries.
Lizards sun themselves on the warm concrete in the summer, and the bunkers also provide shelter for spiders and a wide variety of insects. Mosses and other types of plant thrive on the chalk seeping from the walls.
The Westwall -- the Allies referred to it as the Siegfried Line -- was built between 1936 and 1940. It provided employment for thousands of workers and the Nazi propaganda machine conveyed the mistaken impression that Germany was getting an "unbreachable fortification in the West", as newspapers at the time put it.
Before the war, Nazi spin doctors pointed to the Westwall as evidence that Germany's intentions were purely defensive. After the fighting began, its purpose was to protect Germany's western flank while Hitler sought "lebensraum" in the east.
The bunkers didn't play a military role until after the Allied landings in Normandy in 1944. Advancing US troops encountered fierce resistance in the narrow valleys of the Huertgenwald forest near Aachen in late 1944 which claimed the lives of an estimated 35,000 US soldiers and 12,000-15,000 German defenders.
The Westwall also became a staging area for German forces ahead of the Battle of the Bulge, Hitler's last major offensive of the war. Despite all the propaganda, the bunkers were largely irrelevant as an obstacle in the final months of the war because the Allies had air superiority. In fact, they became death traps for many German soldiers because their walls often didn't withstand shelling.
In a bid to preserve the bunkers, wildlife group BUND has joined forces with regional monument conservation agencies which have been arguing that the Siegfried Line is worth keeping intact because of its historical significance.
Some 100 of the estimated 2,000 bunkers in the state of North Rhine-Westphalia have already been placed under monument protection and local historians provide tours of some of them.
There are thousands more bunkers in the other German states through which the Westwall runs -- Rhineland-Palatinate, Baden-Württemberg and Saarland. So far, efforts to preserve them have been on a regional basis and there has been no nationwide approach.
Schöne says the lobbying is starting to have an effect on the government in Berlin, though. The German Finance Ministry, which owns the bunkers as legal proprietor of all former Nazi state property, is likely to extend a 2004 moratorium on razing the Westwall.
"The federal government is feeling the pressure," he told SPIEGEL ONLINE. "You can't come to terms with history by resorting to bulldozers."
"It's been hard for us to deal with this issue because in Germany you're immediately labeled as some kind of neo-Nazi if you say anything positive about the bunkers. We're accused of trivializing history by calling it 'Green Wall in the West'. But we're not saying the Westwall is great. We're just being pragmatic."
Schöne gave SPIEGEL ONLINE a tour of some ruined Westwall bunkers on a wooded hill near the town of Nettersheim southwest of Cologne. "We've spotted bats in this one," he said, pointing inside one cavernous underground room with rusting iron rods jutting out of the ceiling. Unfortunately, none were visible, but it was during the daytime so they were probably sleeping.
Schöne has personally inspected 400 bunkers to check them for wildlife, and he wrote a report on their value as a natural habitat. He has received €200,000 of funding for the project over the last two years, mostly from regional government funds, and said he had received verbal assurances that the project would get more financing.
Wildcats Give Helping Paw
Schöne said BUND had bought one bunker for €7,000 to ensure it wasn't torn down. Local councils are also starting to get involved, with the nearby town of Euskirchen recently purchasing six bunkers that had been destined for removal even though they were designated as a protected habitat under EU rules.
"Local authorities have realized their potential as a tourist attraction that could generate money," said Schöne. The alliance between local councils and wildlife groups is likely to be an uneasy one though, given that bats and wildcats won't appreciate tour groups.
"We don't want to attract too many visitors," said Schöne, who favors channeling tourists through some selected bunkers that don't have wildlife, or confining tours to seasons when the bunkers are empty.
In one recent case, the wildlife itself took over the lobbying, with immediate success.
"Recently some local officials met to inspect a bunker to see whether it was worth preserving. They were just about to go in when they spotted two wildcats dashing out of it. That saved the bunker," Schöne said.