The Battle of Grand Gulf was fought on April 29, 1863, during th: The United Kingdom lies between latitudes 49° and 61° N, and longitudes 9° W and 2° E. Northern Ireland shares a 224-mile (360 km) land boundary with the Republic of Ireland.[136] The coastline of Great Britain is 11,073 miles (17,820 km) long.[139] It is connected to continental Europe by the Channel Tunnel, which at 31 miles (50 km) (24 miles (38 km) underwater) is the longest underwater tunnel in the world.[140]