Bouldering is a sport where people climb a wall without using a rope. Eventhough this sounds very dangerous, it is not as dangerous as free soloing because the height limit tends to be around 4.5m. Being shorter in length, boulder problems tend to be more (physically) demanding than climbing routes of similar grades and often include features such as overhangs or roofs.
The latest addition to the climbing halls in Groningen is Apex Boulders. The hall does not only have boulder walls for all different climbing styles, but also offers training facilities such as a kilter board and a gym. With around 200 problems there are boulders for every level from beginner to expert.
As a GSAC member you can boulder at a discounted price:
Entrance on the GSAC evening (first Friday of the month, 18:00 onwards): €7,50
Monthly subscription: €47.50
10x entrance: €85.50
Additionally, A GSAC boulder training is given by Frank on Thursdays, which you can join for the discounted price of €7,50.