London is the capital of the United Kingdom and of England, and with over seven million inhabitants in the Greater London area, is the second-most populous conurbation in Europe (after Moscow). From being Londinium, the capital of the Roman province of Britannia, it rose to become the centre of the British Empire and today contributes 17% of the GDP of the UK's economy, the world's fourth largest. London has been one of the world's most important centres of commerce and politics for several centuries. Today the Greater London administrative area comprises the City of London and 32 London boroughs including the City of Westminster. The City of London, also known as the "square mile", is predominantly the financial centre, and geographically a very small area. Although bustling during the working week, the City of London is usually much calmer on the weekends.