Manchester is northwest of England's capital, London. The city has many canals and rivers which were important to its growth, especially in the 18th and 19th centuries. The largest open space in the city is Heaton Park. It has an area of about . Heaton Park is a place that attracts many people every year. People go there to see the many animals and the beauty of the countryside. Much of Manchester is built-up (or 'urbanised'). Much of Manchester's rain comes over from the Pennines, which are hills to the east of the city. The city is mainly urban areas but also has some areas which are mainly of farmland. To the south of the centre is Manchester Airport. This is the third largest airport in the United Kingdom.