My colleague Harry unfortunately can't take part in the Fietselfstedentocht this year, so he offered me his entry form, which I've very gratefully accepted.
The 240 km long ride is limited to 15000 entrants. The population of the country is around 16 million, so nearly one in a thousand people from the Netherlands take part in this event each year. The event has been held every year since 1912, except in 2001 when an outbreak of Foot and Mouth disease caused cancellation.
I'll be riding my Mango over the course. It's now a touring event, not a race, and the 25 km/h maximum allowed average speed means no real advantage from aerodynamics, but it's comfortable to ride in the Mango.
We'll be setting off in 23 groups of 600 people at a time, each group starting eight minutes apart between 5:00 and 8:00 on the morning of the 24th of May. I'm in group 8, which means starting at 5:56.
My plan is to ride to Bolsward the day before with my tent and perhaps return the day after the event. It's about 85 km from here.
The official website of the Fietselfstedentocht is here.
The original Elfstedentocht, dating back to 1909, is an ice skating event over 200 km which is named for the Eleven Cities ("Elf Steden") that the frozen canals pass through. This event is only held on winters which get cold enough (last winter the canals and lakes froze enough for skating, but not enough for the elfstedentocht).
The 1963 Elfstedentocht, the coldest and most difficult in history, was recently the subject of a very enjoyable film.
There are also Elfstedentochts by roller skate and scooter (pushing with one foot, not with an engine) so by taking part in the cycling version I feel I'm definitely taking the easy option.
The Dutch version of the wikipedia page has more information.