The largest train junction in Europe. Clapham Junction is located in Clapham, in the south of London. It is used for trains to get from anywhere in Britain to London, this results in the odd situation that for a train to get from A to B it is often obliged to pass through Clapham Junction, despite the fact London is (by a long a way!) not the geographical center of island of Great Britain.

However London is by far the most important city in the United Kingdom (if not Europe), which results in a heavy emphasis on making sure everywhere connects to London, rather than logically assisting everywhere to connect to everywhere else. If it wasn't for London this main junction of the UK would probably be based around Birmingham (which is the UK's second largest city and also the dead(ish) center of the island).

The reason the biggest junction of Europe is located in a medium sized island instead of on the huge continental landmass is worth pondering, it's due to the UK having the first rush of railway "planning" after suddenly inventing of the train. Things just happened to bunch up in South London, whereas in Europe - despite the fact you had 20 nations with international railroads in operation - had more time and space to plan their junctions.
