Not for the inexperienced, mountain climbing is one of the most extreme forms of adventure travel and should only be done with proper training. Not only does mountain climbing often incorporate the use of tools, like ropes and picks, to scale cliffs but it also requires climbers to know the dangers of high altitude. For a less dangerous yet still thrilling adrenaline rush, try coasterring. This activity combines rock climbing, swimming and cliff jumping and has been gaining in popularity in Europe. While you should still be in good physical condition, it doesn't require as much training as actual mountain climbing.