Birmingham is the second city of the United Kingdom and part of the West Midlands metropolis. It is the second largest city in the UK and forms the bulk of the West Midlands along with the cities of Wolverhampton, Walsall and others. Birmingham acts as a regional centre for the midlands, as well as most of the area between London and the northern cities of Manchester and Liverpool. It is also a transport hub, being the meeting point of the M6, M40 and M5 motorways. It has three central rail stations, serving the West Coast Main Line, Chiltern Main Line and Cross Country Main Line. Birmingham International Airport is located in the south east of the city.