Snowdon is the highest mountain in Wales, at an elevation of 1,085 metres above sea level, and the highest point in the British Isles outside the Scottish Highlands. It is located in Snowdonia National Park in Gwynedd, and has been described as "probably the busiest mountain in Britain". It is designated as a national nature reserve for its rare flora and fauna.
A 1682 survey estimated that the summit of Snowdon was at a height of 3,720 feet ; in 1773, Thomas Pennant quoted a later estimate of 3,568 ft above sea level at Caernarfon.
The unique environment of Snowdon, particularly its rare plants, has led to its designation as a national nature reserve. In addition to plants that are widespread in Snowdonia, Snowdon is home to some plants rarely found elsewhere in Britain.