Banská Štiavnica was an important medieval mining center, producing mostly silver. The first water reservoirs were founded by the local miners in the 15th century. However, the most significant development of tajchy was precipitated by a crisis in the mining industry in the 17th century. The depth of the mines' shafts started to reach below the level of the drainage tunnels. As a result, mines were flooded by ground water. The draining mechanisms of that period were powered by human or animal power, which was too expensive. Due to the prohibitive costs, the Royal Court Chamber in Vienna decided to close the mines in Banská Štiavnica and its surroundings. A mining expert and inventor Jozef Karol Hell challenged the decision, submitting a courageous proposal to rescue mining in his home town. An innovative plan based on the use of tajchy was finally endorsed by Emperor Charles VI.