The tallest of the Welsh mountains.
Snowdonia is the largest national park in Wales, covering the West side of North Wales. Snowdonia has a Welsh name as well; Eryri, a much more magestic name, meaning Land of the Eagles. It was renamed by the English Victorians to Snowdonia (meaning The Place That Gets Snow on it in Winter, 'Cos it's Like Really High and Stuff), because when trying to make it into a tourist attraction, they did not think the other English would want to visit a place they could not pronounce. The English name had existed since before the Victorians, but they were the first to use it in a way that made it become more common than the name given to it by the people who lived there. Perhaps they had mistaken the Welsh "Eryri" for the Welsh "Eira", meaning snow. 300 years ago, Eryri was home to the Golden Eagles, but these have since gone extinct in Wales.
The mountains that Snowdonia is famous for are arranged in several groups or massifs. The Northernmost are the Carneddau. South of them are the Glyderau. South of them is Snowdon. Southwest of Snowdon is Moel Hebog. Southeast of Snowdon are the Moelwynion. South of them is the long chain of the Rhinogydd, with the Arenigau to their East, and the Aranau to their Southeast. To the South is Cadair Idris, with a few smaller mountains surrounding it, at the Southern extreme of the national park. From there, Wales remains gently rolling sheep farming country with almost no mountains, until it reaches the scarps and peaks of the Brecon Beacons over 50 KM to the South. Oh, and for anyone who wishes to claim the Brecon Beacons as part of Mid Wales; I grew up there, it's South Wales. Mid Wales is the relatively flat bit North of the Beacons.
Of the massifs, Snowdon, the Glyderau, Cadair Idris and the Carneddau (in that order) are the most popular, with the Aranau deserving more attention than they get.
East of Snowdonia is the long Llŷn (meaning Picture, as opposed to Llyn meaning Lake) Peninsula, while to the Northeast is a large island called Ynys Môn (or Anglesey for those who insist on renaming things). Various parts of the park contain remnants of the old slate and copper mining industries, and under the farmlands to the East of the park are the limestone and lead mines and the few caves in North Wales.
Curently money comes from (among other things like its sheep farms and vast water supplies) tourism, though it is so wild in most places, you would be forgiven for not realising it. Part of the attraction (or occasionally arrogant rejection from some of them from across the border) is that most people here are bilingual, speaking the North Wales variation of Welsh, and English. However, despite its size, almost none of the Welsh population is here, and are mostly crammed into the English speaking South Wales valleys, which accounts for the extremely low percentage of Welsh speakers.