Caves are natural cavities underground.

Coal precious stones and metals are all mined underground.

Cables crisscross our cities and countryside, hidden from view and less likely to be damaged underground. Many are laid under roads, which is why roads are often dug up..

Water pipes are buried underground to protect them from frost. On the surface they would also get in the way.

Sewers are among the biggest tunnels we dig underground. Some are over ten metres high.

Underground railways are also very big tunnels. By putting railways underground, it helps to reduce congestion and speed up travel times.

Many houses have rooms underground for keeping essential utilities. These rooms are called basements..

It is common to put parking garages underground in cities.

By putting many services underground in cities, a lot of space is saved on the surface.

Video: a video of travelling through a road tunnel is available by clicking the start arrow.