The old mining town of Banská Štiavnica has a unique and ingenious system for the management of water, dating back to the early 1700’s. A complete system of “tajchy”, or reservoirs, with interconnecting racing channels, was built for the accumulation of surface water and also as a source of energy. The energy generated proved invaluable for subterranean water pumping machinery in the local mines; indeed Banská Štiavnica became the most important center of precious metal mining during the Habsburg dynasty. It is thanks to the inventors Matej Kornel Hell and Jozef Karol Hell, as well as the scientist and polymath Samuel Mikovíni that this system was devised. By the end of the 1800’s as many as sixty reservoirs were built, of which twenty-three still exist today. Banská Štiavnica and the “tajchy” are UNESCO World Heritage sites. The stamp depicts the Klinger Tajch. On the FDC is the Wheel from the Mining Museum in Banská Štiavnica. The coupon is issued on the 50th anniversary of the Slovak Academy of Sciences (1953 – 2003), a science and research institute for the advancement of technological, cultural and environmental know-how. Forty-one scientific and scholarly societies are affiliated to the S.A.S. Miniaturesheet of 4 stamps of 4 designs