An example of a website featuring lists of challenge rides includes Active.com
Challenge rides often have lengths of round, impressive sounding numbers like 100km (aka metric century), 100 miles (century), 200km (double metric century), etc., each of which is to be completed in a single day. Alternatively they start and finish at interesting locations (for example: the - Brighton charity ride for the British Heart Foundation , and the Dunwich Dynamo ).
Another popular class of ride is a multi-day trip that spans a state, country or province, such as RAGBRAI in Iowa and the End To End in the United Kingdom .
Challenge rides may be single day or multi-day. Multi-day rides can be differentiated into ones where lodging is provided or not. In the latter case, most rides will include a vehicle to carry your tent, clothing, food, etc.