Birmingham is a city and metropolitan borough in the West Midlands, England. It is the largest and most populous British city outside London. The city is a major international commercial centre, ranked as a beta− world city by the Globalization and World Cities Research Network; and an important transport, retail, events and conference hub. The city lies within the West Midlands Built-up Area, the third most populous built-up area in the United Kingdom. Birmingham has a temperate maritime climate, like much of the British Isles, with average maximum temperatures in summer (July) being around 21.3 °C (70.3 °F); and in winter (January) around 6.7 °C (44.1 °F). A medium-sized market town during the medieval period, Birmingham grew to international prominence in the 18th century at the heart of the Midlands Enlightenment and subsequent Industrial Revolution, which saw the town at the forefront of worldwide advances in science, technology and economic development, producing a series of innovations that laid many of the foundations of modern industrial society.  Its metropolitan economy is the second largest in the United Kingdom with a GDP of $121.1bn (2014), and its six universities make it the largest centre of higher education in the country outside London. Birmingham's major cultural institutions – including the City of Birmingham Symphony Orchestra, the Birmingham Royal Ballet, the Birmingham Repertory Theatre, the Library of Birmingham and the Barber Institute of Fine Arts – enjoy international reputations, and the city has vibrant and influential grassroots art, music, literacy and culinary scenes. Birmingham is the fourth-most visited city in the UK by foreign visitors.