Elfstedentocht

Elfstedentocht (English: Eleven cities tour) is a long-distance tour skating event, almost 200 km long, which is held both as a speed skating competition (with 300 contestants) and a leisure tour (with 16,000 skaters). It is held in the province of Friesland in the north of the Netherlands, leading past all 11 historical cities of the province. The tour is held at most once a year, only when the natural ice along the entire course is at least 15 cm thick; sometimes on consecutive years, other times with gaps that may exceed 20 years. When the ice is suitable, the tour is announced and starts within 48 hours.
Course
The Eleven cities tour, almost 200 km in length, follows a closed or circular route along frozen canals, rivers and lakes visiting the eleven historic Frisian towns: starting in Leeuwarden, Sneek, IJlst, Sloten, Stavoren, Hindeloopen, Workum, Bolsward, Harlingen, Franeker, Dokkum, then returning to the Bonkevaart near Leeuwarden for the finish.
The last tours were held in 1985, 1986 and 1997. All skaters must be members of the Association of the Eleven Frisian Towns. A starting permit and bib is required (€100 in 2017). Skaters must collect a stamp in each city, and at three secret check points, and must finish the course before midnight.
Elfstedentocht Swim
2008 Olympic 10 km marathon swim champion Maarten van der Weijden raised over 5 million euros as he attempted to swim non-stop the 200 km Elfstedentocht course where he swam 163 km in 55 hours to benefit the Dutch Cancer Society (KWF) (the Elfstedentocht Swim).