Store Blåkilde (The great Bluespring) is located south-southwest of Madum lake.
It has previously been regarded as the most waterrich of the springs in the Rold Forest area, and thus Denmark's largest. Recent times, however, places Store Blåkilde after, for example, Gravlev Kilde, Lille Blåkilde(little bluespring) and Ravnkilde (Ravenspring).
The water supply in the main spring is about 80 l per sec. The flow of the water from Store Blåkilde is in certain places measured to be around 300 l / sec.
Store Blåkilde is a typical pool-spring. The bassin is almost oval (about 12 m in the widest place and at a depth of 4-5 m)
Store Blåkildes pure blue color is due to the fact that some of the bottom is bright sand, which in connection with the clear water and the glare of the blue sky, gives the source the distinctively pure blue color.
The clear blue water has probably given the source its name. However, the name may also be derived from an old danish word "Blotkilde" (sacrificial source). Yet again in the last century it was customary that gentlemen from the nearby Villestrup Castle threw some silver coins into the source before they went hunting. A small tax must lie there in the course of the spring.
The spring is protected and according to this, it is strictly forbidden to collect animals as well as to wade in the source.