The tunnel was built during the period 1975 to 1987.
The tunnel was built in the 1840s and cost £90,000.
The two new tunnels were built between 1912 and 1914.
It was also going to be longer than any tunnel yet built.
Any further increase in capacity would only be possible by building a second tunnel through the city center.
The tunnel was built using the cut and cover method.
The tunnel was built in the early 1890s and can be visited today.
They also agree to build a new bridge and tunnel.
The tunnels on the A line were built along with their stations in the late 1920's.
A new tunnel is being built west of Hell, to be finished 2012.