A castle well was often both in terms of construction time as well as the construction cost of the most expensive phase of construction of a castle. Its construction could take part several decades.
The fountain served - in addition to tanks - both in times of peace as well as in cases of siege the castle occupying and possibly also the there seeking protection in wartime civilian population as a safe source of drinking water. She could not also in the siege case be poisoned "from the outside " (well poisoning, for example, by decomposing carcasses were in the Middle Ages often Applied agent to force a garrison for the task).
Was depending on the height of the castle above the groundwater level, particularly in hill forts, often to be overcome a significant height difference, to go to the next sufficiently water-bearing geological layer. In addition, the wells was a problem that supply the well by hand in the rock propelling workers with sufficient oxygen.
To supply the fountain maker with fresh air, a mostly wooden partition was often the center of the well shaft installed, that cracks were sealed air-tight as possible with straw and pitch. Then a fire pit was built above the external fireplace, which drew its air supply from below through the well shaft. The fresh air (and thus oxygen) is circulated through an artificially built underground, in the center of which was the separation wall and the sole of a fresh air stream moved that supplied the workers with sufficient oxygen.
In Germany there are some of the deepest castle well in the world. They can be found on the Empire Kyffhausen (176 meters depth), the fortress Königstein ( 152 meters depth) and High Castle in Homberg (150 meters depth). Finally we have the deepest driven in Basalt fountains in the world at the castle Stolpen (82 meters depth).
According to historical sources, a castle well with a depth of over 197 meters is said to have once been on the Burg Regenstein at Blankenburg. This is spilled for some time.