The most difficult metro riddles

Ventilation shafts at various points on the route allowed the engines to expel steam and bring fresh air into the tunnels. These shafts were sometimes hidden behind false facades, like the one in the photo (Leinster Gardens 23). The right-hand property is a fake.

Serfaus is a municipality in the district of Landeck in the Austrian state of Tyrol. Serfaus is also known for its small hovertrain subway system, the Dorfbahn Serfaus. With four stations and a length of 1280 m (the second-shortest underground train line in the world) it allows for a complete ban of cars within the town, while at the same time maintaining the village's attractiveness to tourists, particularly skiers.

Many stations on the Stockholm metro use organic architecture, which leaves the bedrock exposed and unsculptured, appearing to be based on natural cave systems.

The Metropolitan Railway opened on 10 January 1863, and was carrying over 26,000 passengers a day within a few months of opening. The early lines were built by various private companies, and became integrated in 1933.

The Moscow Metro was one of the USSR’s most extravagant architectural projects. Stalin ordered the metro’s artists and architects to design a structure that embodied a radiant future.