Monceau Metro Station is on line 2 - the second oldest in Paris. The first section of the line opened in 1900, with Monceau itself being operational a couple of years later. Originally Monceau was a destination on the line and a large turning loop was provided to allow trains to reverse.
When this loop became disused, part of the space was converted into a protected operations centre for the Metro for use in World War II. The space also had an air-raid shelter for use by the company’s directors. Post war the operations centre was converted to a training facility.
When Sub Brit visited in 2008, we were able to followed the curved course of the loop to find the now disused accommodation. Part of the Metro utilised underground compressed air as a power source (removing some of the risks of electrical services) and we found a pneumatic sump pump still in operation; powered we believe by a local compressor rather than a wider network.
Most extraordinarily, we then emerged onto a short section of the curve still laid with track. It was here that the directors would have arrived by train and the siding was priotected by still-operational gas-tight doors across the whole track. The line can still be accessed by trains and it held an assortment of pre-war carriages awaiting restoration and display.