Loch Lomond and the Trossachs National Park straddle the highland boundary fault between the lowlands and highlands of Scotland.  Some consider Loch Lomond the jewel of the National Park.  Loch Lomond is the largest body of inland water in the United Kingdom, covering over 27 square miles.  It is 23 miles long, the second longest to Loch Ness and at 623ft, the third deepest after Loch Morar and Loch Less.  Before the thirteenth century it was known as Loch Levan or Levand from the vale of the river Leven, the only outlet from Balloch in the south to Dumbarton on the Clyde.  The southern end of the loch is only four miles from tidal waters, and the northern end just less than two miles from the sea loch in Loch Long at Arrochar.