© Slovenská pošta, a.s., 2006 Slovakia, despite its relatively small area, is characterised by a very diverse and complicated geological structure. Endogenous and exogenous processes continually repeating and alternating with each other have determined - during their intricate evolution - the variability of the rock. The important part of the endogenous processes is volcanic activity, the result of which is the birth of volcanoes that have produced a wide spectrum of volcanic rocks. Under the influence of changes of climatic factors (temperature, wind, precipitation), the exogenous processes cause the weathering of rock surface layers, and transport the products of such erosion with water and air onto the places of their repeated accumulation and subsequent building up of new sedimentary rocks. Under the influence of just the above-mentioned phenomena, many unique natural formations have emerged in Slovakia. One such formation, “the stone basalt waterfall” at castle hill Šomoška, is reproduced on both a Slovak postage stamp and FDC. This formation represents the selectively preserved part of basalt lava intake canal (neku) with distinctive mildly bent columnar jointing. Šomoška is situated in Cerová upland, the municipality of Šiatorošská Bukovinka (post office Radzovce), near the Slovak-Hungary border. It is a national nature reserve with an area of about 90 acres, and with a nature trail passing through it. Sea sediments (mostly sandstones) prevail in the lower parts of the geologic structure Cerová upland which evidences the former presence of a sea bay. Volcanic activity is represented by less frequent older andesites (15.5 to 16.5 million years) – in the vicinity of Šiatorošská Bukovinka. But younger basalts (5 to 1.2 million years) prevail, forming peaks and extended crests in the west part of upland. The territory of Cerová upland is an outstanding phenomenon of both inanimate and animated nature summarily written up in the popular scientific work “Geological educational map of Cerová upland in scale 1 : 50 000 (RNDr. M. Elečko, CSc et al.)”. This was published by the Dionýz Štúr National Geological Institute in cooperation with the Ministry of Environment of the Slovak Republic in 2001. RNDr. Karol Marsina, CSc