Der Spiegel reports an attack may have been planned on the historic building . The United States issued a general travel alert for Americans in Europe last month amid concerns that al Qaeda or related groups might be planning attacks similar to the 2008 massacre in the Indian city of Mumbai . The newspaper does not identify its sources . The building is a top tourist attraction .
Der Spiegel reports an attack may have been planned on the historic building . The newspaper does not identify its sources . The building is a top tourist attraction .