It resembles an amusement park ride, but the Falkirk Wheel in Falkirk, Scotland, is the world’s only revolving boatlift. It opened in May 2002, and now performs a task that previously  required 11 locks: moving boats along the 35 meters of vertical height between the Forth and Clyde and the Union canals.

Although it’s called a wheel, the Falkirk is not round. It consists of two large, identical steel arms 28 meters apart, which rotate on an axle speared though their centers. The arms support two 26.5-meter long, water-filled tubs, or gondolas-one at the top and one at the bottom.

A 30-centimeter gap between the gondola and the end of the waterway must be filled with water before a boat can enter.  Bellows-like seals expand to form a watertight connection between the waterway and the gondola. A valve allows water to fill the gap. When the water levels inside and outside the gondola are even, doors open, allowing the boat to enter. The doors close, and pumps drain the water from the gap. The wheel is then free to turn.

The Falkirk Wheel’s stats are Herculean. The twin arms with their gondolas weigh a combined 1,300 metric tons. Each gondola carries about 250,000 liters of water and can accommodate as many as four 10-meter boats. Boaters at the top have a 50-kilometer view of the countryside. In fact, it’s the only place where the best view of Scotland is from the helm of a boat.