Gustav Dore's etching of the London Underground circa 1870.
Here are some facts about the Tube that you might not know.
1. The most popular route for tourists is Leicester Square to Covent Garden on the Piccadilly line. It is quicker to walk this distance than travel on the tube.
2. The oldest tube line in the world is the Metropolitan Line. If you happen to sit in one of the older carriages on this line you won't be surprised by this fact. It opened on January 10th 1863.
3. Northfields station on the Piccadilly line was the first to use kestrels and hawks to kill
pigeons and stop them setting up homes in stations.
4. There are only two tube stations which have all five vowels in them - Mansion House and South Ealing.
5. More than 50% of the London Underground runs above ground.
6. The 409 escalators on the Underground network do the equivalent of two round the world trips every week.
7. The Northern Line station at Angel has Western Europe's longest escalator - 318 steps.
8. The most popular station to watch mice on the tracks is Oxford Circus.
9. The originally Tube carriages had no windows and buttoned upholstery. Unsurprisingly they were known as padded cells.
10. Thousands of Londoners used the London Underground as a shelter during the London Blitz from September 1940 to May 1941.
Photo of Londoners spending the night in the Tube during the Blitz courtesy http://en.widipedia.org.