A canal tunnel is a tunnel

Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...

 for a canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

. The biggest canal tunnel in the world is the Rove Tunnel

Rove Tunnel

The Rove Tunnel is a canal tunnel in France. It is about 4.5 mi long and 72 ft wide and opened in 1927. The Rove Tunnel remains the biggest canal tunnel in the world. The tunnel was closed in 1963 after its collapse....

 in France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. The oldest canal tunnel in the world is the Malpas Tunnel

Malpas Tunnel

The Malpas tunnel was excavated in 1679 under the hill d'Ensérune in Hérault, allowing the passage of the Canal du Midi. It was Europe's first navigable canal tunnel and a monument to the determination of Pierre-Paul Riquet, the chief engineer. It is located in the commune of Nissan-lez-Ensérune...

 also in France, built in 1679. In the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 there is the Paw Paw Tunnel

Paw Paw Tunnel

The Paw Paw Tunnel is a long canal tunnel on the Chesapeake and Ohio Canal in Allegany County, Maryland. Located near Paw Paw, West Virginia, it was built to bypass the Paw-Paw Bends, a six-mile stretch of the Potomac River containing five horseshoe bends...

 that opened in 1850.

In some canal tunnels the towpath

Towpath

A towpath is a road or trail on the bank of a river, canal, or other inland waterway. The purpose of a towpath is to allow a land vehicle, beasts of burden, or a team of human pullers to tow a boat, often a barge...

 continues through the tunnel. In other cases, especially on English narrow canals, there is no towpath. The horse would be led over the hill and the boat would be propelled by legging

Legging (canals)

Legging is a method of moving a boat through a canal tunnel or adit containing water.-Legging in canal tunnels:Early canal tunnels were built without a towpath as this would require a much larger bore, and hence cost more to build. Prior to the introduction of motorised boats, legging was one of...

.

Sources

• Rove Tunnel at Wikimapia
• Canal du Midi