Aufklärungsturm A, Observation tower in Klaustorf, Schleswig-Holstein, Germany

Aufklärungsturm A is a concrete structure near Großenbrode with 16 floors originally containing offices, workshops, and personnel quarters. The building rises approximately 105 meters above sea level and now provides visitors with access to an observation deck on the seventh floor.

Turm A was built between 1965 and 1968 as one of five Luftwaffe reconnaissance towers along the German-German border, operated by Fernmeldesektor A of Fernmelderegiment 71, whose soldiers were housed in the Fehmarnsundkaserne at Großenbrode. It was decommissioned in 2004, sold to the Meereszentrum Fehmarn and renamed Ocean Tower in 2005. The Ostsee Erlebniswelt opened in the horizontal extension in 2012, and in 2023 the name changed to Ostsee Aussichtsturm Klaustorf.

The tower's name reflects its past role as a reconnaissance station, yet today it functions as a learning center for visitors. This shift shows how the region transformed military spaces into places for education and recreation.

The tower stands east of the E47 between Heiligenhafen and the Fehmarnsund Bridge, on a natural rise in Klaustorf. The balcony around the 7th floor, more than 80 metres above sea level, has been open as a viewing platform since July 2017. The Ostsee Erlebniswelt in the adjoining horizontal extension opened in 2012 and houses the Ostsee theme exhibition.

The tower's nickname Spökenkieker (Low German for "fortune-teller" or "ghost-seer") came from its listening role: from the 8th floor directional radio was intercepted, and floors 10 and 11 held signals-intelligence posts and equipment for recording radar emissions. From 1987 the LAPAS high-altitude reconnaissance programme added the low horizontal annexe beside the shaft.