Sheffield is the largest city (575,000 inhabitants) in the county of South Yorkshire. Once known for its vast steel production, this has sharply declined since the 1960s. The local economy is now more characterised by services and advanced manufacturing. Sheffield University is one of the leading research universities in the UK and, together with other local universities, has helped to drive industrial innovation. Sheffield is also known for its parks and green spaces. The city is estimated to contain over 2 million trees, the most per capita of any city in Europe.