There are an abundance of long distance "challenge" walks held all over the world. The longer distances range from 40km to over 160km. Of course, there are many shorter walks as well.
These are not judged races but they do aim to test your endurance over distances in a given timescale and the challenge usually is the actual distance and very often the terrain - road, pavement, off road (often muddy footpaths...!)
Europe holds many challenge walks hosted by clubs and organisations such as, Eurodax, Rotterdam Walking Club (RWV) and OLAT walking club.
The RWV and OLAT clubs host the Continental Centurions races as well as shorter races 80km and social walks.
A very popular walk is the 160km/100 miles Nijmegen to Rotterdam walk (time limit 28 hours) held every September and organised by the RWV. This is a "led" walk with time limits to reach each control point. Feed stations are provided and kit bags are transported along the route. A sit down, hot meal is provided at half way. Usually about 70 walkers take part - many of them Centurions.
Other challenge walks to look out for, are the ones organised by the International Marching League (IML) usually 2 or 3 day walks of 30km/40km distances which are held throughout the world.
The UK has the Long Distance Walking Association (LDWA) which puts on walks ranging from 15 miles up to 100 miles - many of these are off-road. Some of the shorter walks are "social walks" with a group leader; other walks need some navigation skills or the ability to follow a route description.
The Ramblers are another UK group which organise shorter and slower walks, and are a very "environmental focussed " group as well.
The Netherlands is famous for the Vierdaagse - Four Days march (distances of 30km, 40km and 50km). The event is held in July and many Dutch, Belgian, UK Centurions take part every year (Danish and Australian Centurions have been spotted taking part as well!)
Dutch ex-pats living in Spain have there own version of the Vierdaagse called the 4DaysWalking which is held in Marbella every October - distances range from 10km to 30km each day.
Another popular walk is the 100km Dodentocht (Death March) which is an overnight walk starting in Bornem (near Antwerp), Belgium. Mostly on road and it's a great experience! Up to 15,000 runners and walkers take part - many are Centurions from Holland, Belgium and the UK.
Whether a "challenge" walk, a 50km race or something shorter or longer... they are all good training events (as well as good fun!) and many Centurions will be there!
And if you know of a good one...let us know!