The bouldering is climbing on large stones that are generally about 4-5 meters high. To secure the climber, are using a mattress (crash pad) to land on in case of fall. Sometimes the height can reach even 10 meters (high bouldering). Then the fall may cause fatal or serious injuries. High bouldering in only for many experienced climbers. Overall Boulder is a social activity in which can participate lot of people as those who do not climb are spotting the climber in order not to fall over on his/her back or side, where he/she can get hurt. The goal is that each fall is followed by a controlled landing with the feet down on the soft mat. Practicing bouldering in a hall is much safer than real rock. Mattresses in the room are very thick and even uncontrolled fall is not dangerous. On a real terrain, however, the statistic shows that boulder contributes to more injuries in comparison to sports climbing. However, many people prefer to practice bouldering because of the low cost of equipment compared to other types of climbing (just pair of shoes and chalk bag).
The most popular areas for practicing a boulder are in Rila and Vitosha, some are so close that they are suitable to be visited in long summer days after working hours. Many lines are set, but of course everything is a matter of imagination. Each line you choose on the rock could be your buolder problem.