The Great Glen Cycle Route runs from Fort William to Inverness. Fort William to South Laggan is mostly easy. Much of it is on the Caledonian Canal Towpath and the towpath section is traffic free. Later parts of the route, north-east of Laggan, are very hilly, with long climbs and steep descents. The final section to Inverness involves some road cycling.
There is also a walking route, the Great Glen Way. Most of this is the same as the cycle route but a few parts are different and these are walking only.
The Great Glen forms the dividing line between the Northern Highlands and the Central Highlands. The Great Glen watershed is only 35 metres above sea level. The Cycle Route climbs much higher than this, to over 300 metres at times.
The Caledonian Canal which joins the series of lochs in the Great Glen was designed by Thomas Telford and completed in 1822. The spectacular scenery is unusual for a canal, particularly the massif of Ben Nevis, the highest hill in Scotland (1345m). The summit is only four miles from the sea and the full sense of its height can be appreciated from the cycle route. It has the highest sheer cliff face in Britain (1500ft), and virtually the only semi-permanent snow patch.
The Great Glen Cycle Route continues up the west side of Loch Ness but you should be aware that north of Drumnadrochit you have to cycle on public roads. Most of these are extremely hilly, the only alternative on the west side is the A82 which has heavy traffic.
The other possibility is to cycle on back roads on the east side of Loch Ness. These are quiet. At the time of writing there are discussions between the Forestry Commission, the local authority, and Sustrans about changing the route to the east side of the loch, it seems possible that this will happen. In the meantime both routes are shown.