Myself and Aggravated Trespass had a look around here at the weekend. The top tunnel was built as a countermining gallery for Crownhill Fort in the 1860's. If the crafty French tried to tunnel in from the north, we could blow them up with charges in tunnels of our own, Ha!
This scheme was greatly enhanced by intersecting two east-west tunnels which carried the Plymouth and Devonport leats, bringing fresh water from Dartmoor into the towns.
The higher of the two leats is the Plymouth one which Sir Francis Drake had built in 1590-91 (construction was held up by the war with Spain and the Armada!). The lower Devonport leat was built in the 1790's.
The countermining gallery is built with walls of local stone with a brick vaulted roof, in a similar way to those built inside the forts. The tunnels for the leats are semi-circular arches of local stone, parts of which have been covered with a cement surface. Where they near the ends the roof is made from huge slabs of stone, making it look a bit like a neolithic tomb. At one end (near McDonalds) there is a small collapse providing a much more interesting way in and out.
This scheme was greatly enhanced by intersecting two east-west tunnels which carried the Plymouth and Devonport leats, bringing fresh water from Dartmoor into the towns.
The higher of the two leats is the Plymouth one which Sir Francis Drake had built in 1590-91 (construction was held up by the war with Spain and the Armada!). The lower Devonport leat was built in the 1790's.
The countermining gallery is built with walls of local stone with a brick vaulted roof, in a similar way to those built inside the forts. The tunnels for the leats are semi-circular arches of local stone, parts of which have been covered with a cement surface. Where they near the ends the roof is made from huge slabs of stone, making it look a bit like a neolithic tomb. At one end (near McDonalds) there is a small collapse providing a much more interesting way in and out.
