There is a programme on the History Channel that is called the Cities of the Underworld. I have only just started watching them but it is very good. The premis is a reporter is guided around secret and forgotten tunnels and caverns.
Edinburgh
This episode was very close to home. It described Mary Kings Close and was quite fascinating because I have been in this underground city. Very cool .
A tales of underground limestone quarries dating back from Roman times. The quarries went further underground the caves became dangerous and needed reinforcing. The death toll for workers was very high!
There are also:
World War bomb bunkers
Aquaducts
Sewers
Grafitti dens
Roman Town
Catacombs with over 6million dead buried there. 3 times the number of living people in Paris.
Very cool.
Oh and there was a Professor George Wanklin. Nice.
I would also recommend this series- very interesting. Although my recent discovery of all the documentary channels on sky has lead to a rather full sky plus box
The Paris Catacombs are actually really dangerous to access at night due to the suberlerous (can't spell) crowd they attract - prositutes and thrill seekers mainly. Please note this is not due to personal experience but information lifted from the lonely planet guide!
This episode focused on the underground sewers and catacombs of Rome. It was quite interesting as part of the 2000 year old sewers (which are a template for every modern day city) are still in use and stinking to high heaven. It was the classic tale of the original sewer being an open topped channel used to dispose of waste and also to dispose of ground water (Rome was built in a swamp) and then slowly being built over when space became an issue.
They also have very clever filters for the fresh water supply. Aqueducts fed these huge circular brick and waterproof concrete structures which were subdivided into semi-circular chambers with movement holes. The structure was innovative because it used a type of construction that sandwiched two materials, both very good in compression, to resist the huge pressure of the water. The internal sub-divisions also helped to slow the water and let sediments settle in the bottom of the tank, thus purifying the water. Very clever stuff.