At 117 miles, the M25 or London Orbital Motorway is the second longest city bypass in Europe. The longest is the Berliner Ring, which is 122 miles (196 km) long.
(A Royal Commission first suggested a ring road for London in 1905, but it didn’t happen until the M25 opened on 29th October 1986. It took more than 11 years to actually build, and construction cost £1bn. It used more than two million tonnes of concrete and 3.5 million tonnes of asphalt.