The Great Glen Fault is one of the most significant geological features in Britain. It runs in an almost perfectly straight line from Inverness on the Moray Firth to Fort William on the Atlantic coast, a distance of approximately 62 miles. Loch Ness occupies the deepest section of this fault-line trench, its bed scoured by successive ice ages to well below sea level. The loch never freezes -- the volume of water is too great and the thermal mass too stable for surface ice to form. Thomas Telford's Caledonian Canal, completed in 1822 after nearly two decades of construction, linked Loch Ness with Loch Oich and Loch Lochy to create a navigable waterway from coast to coast. The canal's twenty-nine locks raise and lower vessels across the Highland watershed, but the three natural lochs provide most of the canal's length, with Loch Ness alone contributing twenty-three of the canal's sixty-mile route.

A complete circuit of Loch Ness covers approximately seventy miles, with the A82 following the western shore and the B862 and B852 taking the quieter eastern side. The western road passes through Drumnadrochit, where Urquhart Castle stands on a headland above the water -- a ruined medieval fortress that has changed hands more times than any other castle in Scotland. General Wade's military road, built in the 1720s to move troops rapidly through the Highlands after the Jacobite risings, follows parts of the eastern shore, and stretches of the original surface survive. The eastern side of the loch sees far fewer tourists and offers a different experience: single-track roads, scattered crofting townships, and views across the water to the mountains on the far side. Falls of Foyers, a waterfall that drops 144 feet in two stages, is accessible from the eastern road and was visited by Robert Burns in 1787, who composed a poem on the spot.

The monster industry is concentrated at Drumnadrochit, where competing exhibition centres present the Nessie legend with varying degrees of credulity. But Loch Ness rewards visitors who look beyond the creature. Fort Augustus, at the loch's southwestern end, offers the spectacle of boats passing through the Caledonian Canal's staircase locks -- a system of engineering that raises vessels between Loch Oich and Loch Ness in a sequence of water-filled chambers. Invermoriston, on the western shore, has a fine old bridge and the remains of a Columban monastery. The loch itself, seen from the water on one of the cruise boats or from the hills above its shores, is genuinely atmospheric: the dark water, the steep wooded banks, the cloud patterns that form and dissolve over its surface. On still days the reflections are perfect. On stormy days the loch earns its reputation -- waves can build to surprising heights in the fetch between the enclosing hills, and the dark water takes on a character that makes monster stories feel less absurd than they sound in print.