When the 200-foot tall dish telescope in Green Bank, West Virginia needed receiver maintenance, operators drove its 140-foot (43-meter) dish to within four feet of the ground. An engineering tower was winched up until the apex of the telescope was nestled inside. Then, in a protected space, the sensitive equipment was removed, replaced, and finely adjusted. These days, the 140-foot has not been using a receiver at its apex. Instead, a sophisticated second reflector sits here to bounce waves to receivers nestled in the hole in the center of the dish. The tower is still used to work on the apex.