Rubjerg Knude Lighthouse, Hjørring, Denmark

Jutting out from a desolate dune called Lønstrup Klint (cliff), this ghostly sentinel was built in 1900 but abandoned in 1968 after sands and sea began to devour it whole. The sturdy 75-foot-tall building will likely collapse from shifting sands and coastal erosion in the next decade—and it makes you wonder what other ancient Viking relics lie beneath the sand.

Mystery: The tower was built on a dune-less cliff 656 feet from the sea and nearly 200-feet above sea level, yet, despite rescue attempts, the elements slowly swallowed it over the years.

Visit: Twenty miles north is a Danish Modernist country house steps from a more tranquil beach.

Unusual Buildings