Scotland's most famous viaduct (no one I ask can think of a runner-up) sneaks up on you. It is a curved construction that leans into the landscape beyond and can be glimpsed only briefly as the train thunders over it.
For more than a century, the railway line that crosses the viaduct and connects the West Highlands to Scotland's largest city, Glasgow, was a crucial, yet underused link. So remote is this part of the country there was talk a few years ago of closing down the station in Glenfinnan, which lies about halfway between Mallaig and Fort William.
Glenfinnan's fortunes turned, however, when a boy wizard named Harry Potter boarded the Hogwarts Express and rode across the same viaduct to begin each term at the school of witchcraft and wizardry. Today, fans of the Harry Potter series can take The Jacobite steam train - which includes some of the carriages seen in the films - along track depicted in scenes such as the flying-car sequence.
When the train conductor announces that the viaduct is approaching, passengers rush to the side to get a glimpse through thick, grimy windows.
'Hogwarts!' yells an overexcited fan scrambling to the left side of the train as it arrives at the station.
Glenfinnan itself does little to market its connection to Harry Potter, even though a recent poll ranked Hogwarts as the 36th best Scottish educational establishment after it was listed for fun and then voted on by the public.