The London Eye, located on the South Bank of the Thames, is an observation wheel that works in a similar way to a bicycle or Ferris wheel, using a cantilevered rotating structure with passenger capsules attached to the frame. The structure consists of a 135m high carbon steel wheel rim joined to a central two-legged A-Frame using 16 rim rotation cables and 64 spoke cables. The A-Frame is a 70m long carbon steel tower locked into a compression foundation that maintains the wheel's balance. A 25m long spindle is attached to the A-Frame, and maintains the electronically powered rotation of the wheel. 32 passenger capsules are attached to the outside of the rim, and remain at a stationary angle while the wheel rotates. The capsules are egg-shaped in order to reduce wind-drag, and have a width of 4m. The Eye was designed and constructed by Marks Barfield Architects and is currently the largest example of its type in the world.