Cumbria is a County of diverse landscapes, which reflect a complex geology. The physical geography of Cumbria is dominated by a central ‘dome’ of high relief which forms most of the Lake District National Park. Cumbria’s sixteen lakes fall within this area. Many of the County's rivers originate from here and radiate outwards. However, the County's longest river, the Eden, rises in the Pennines and flows towards the Solway Firth, across one of the substantial lowland valleys to be found around the central ‘dome’. A substantial part of Cumbria lies above 300 metres and this mass of land physically divides the County from north to south and east to west. For days out there are lakes you can take cruises on such as Lake Windermere, for museums there is the Haig Collery Mining Museum, the RAF Millom Museum and Windermere Steamboat Museum. For the historian and gardener there is Sizergh Castle and Gardens and Muncaster Castle where you can also enjoy a visit to the World Owl Trust. The County boundary is naturally defined by the Irish Sea to the West, from the Solway Firth to Morecambe Bay, with the Scottish border to the north and the Pennine hills to the east.