Archaeologists carrying out conservation work on Greece's most prized monument have hit on a new extreme sport, one unlikely to feature in visitor tours anytime soon - rappelling down the walls of the Acropolis, the ancient citadel overlooking Athens.

Part of an operation to determine the condition of the walls -- which are over 2,300 years old -- the stunt teamed up conservation experts with veteran mountaineers enlisted to place electrode sensors onto the citadel's southern side, a senior archaeologist said Sunday.

Maria Ioannidou, the senior archeologist in charge of conservation work on the Acropolis, said the sensor readings would be used to compile a geological scan of the walls, and detect possible damage caused by centuries of soil erosion and water seepage.

"The original surface of the citadel was much higher, what we see today is the result of several excavations," Ioannidou told AFP. "As a result, there is the possibility of water seeping into the walls. But there is no reason for concern, we are just inspecting the wall's condition at this stage," she added.

The climb down the 18-metre (59-foot) southern wall was completed last week, with assistance from Greek mountaineers Michalis Styllas and Vassilis Naxakis, who were brought in by the geophysics department of the Salonika-based Aristotelio University.

Styllas was part of a Greek team that placed the flag of the Athens 2004 Olympics at the summit of
Mount Everest in May 2004.

"We had to place the electrodes properly," he told NET state television. "I'm really curious to see the results."

This is the first time that archaeologists will have access to a vertical reading of the Acropolis walls, as all past scans were conducted on the citadel's surface, Ioannidou said.