Adventure races are difficiult to define, but in general they are multidiscipline team events with a broad variety. On the smaller scale, there are urban obstacle courses over only a couple of hours but still with plenty of challenges. An example of an urban adventure race is the popular Rat Race series. More frequently, adventure races take place in more extreme locations in the countryside. These races go off-road and can take place over several days. These events often resemble military training camps, and in the UK can take you across national parks, mountain ranges, and from coast to coast. Organisers can include any number of sports but the core disciplines that tend to be required are: trail running, mountain biking, open-water swimming, and kayaking. The terrains chosen are often tricky and isolated, so you will also have to call upon your navigation skills either on your own or as part of a team. Some races aren't standard point-to-point races, but instead require you to reach as many checkpoints as possible within a given time limit. Adventure races are not for the faint-hearted, and are a real test of human endurance against nature.