In a century of operations, coal mining in the German town of Goitzsche took out 315 million tons of lignite; that leaves a lot of big holes in the ground. The remediation plan included flooding ten square miles of it to create recreational lakes. As a "symbol of the demise of the 20th century industrial world" and to "denote a transition toward respect for earth, water and air," (and as a tourist attraction) they built a pegelterm, or water level tower, 85 feet high, with a double helical staircase, one up and one down, spiralling around it. A giant stainless steel pin is anchored into the ground and the entire stainless steel tower floats, like an oversized sock moving on the pin and rising with the water. It was all built with very little waste, is maintenance free and 100% recyclable. ::Eco-structure and ::Mevaco
"That's because the core of the Pegelturm is a 20 m long tubular steel plug which is firmly anchored into the ground. The actual tower itself stands on a floating platform made of sheet steel. Its shaft, a frame construction comprising eight vertical girders covered with perforated sheets, is only connected to the plug via slide bearings. As the lake was flooded, the tower grew out of the plug like a telescope, a process which could be followed from the bank thanks to the increasing transparency of the perforated sheets. The sheet steel stair strings are bolted to the perforated sheet shaft. Two contrarotating spiral staircases create a separate entrance and exit in the Pegelturm. When the lake was flooded, two openings were created as a passageway between the staircases. The safety of visitors is ensured by a steel net surrounding the tower."