The arc of the Carpathians to the E and N, the extreme offshoots of the Eastern Alps to the W, the external slope of the Dinaric system to the S enclose one of the largest tectonic depressions in Europe, the Pannonian basin (or plain), which, included in mostly within the borders of Hungary, determines the dominant aspect of the landscape; however, due to the complex geological events that have gradually shaped it and the different composition of the soil, it is less monotonous than one might suppose. The depression, crossed today from N to S by the Danube and its tributary Tisza, was formed in the Cenozoic era towards the end of the Alpine orogeny; the tectonic sinking was accompanied by volcanic phenomena at the edge of the plain itself, of which secondary manifestations still remain today in the form, for example, of those thermal springs of which the country is so rich. Invaded by the sea, the Hungarian plain became an immense closed basin, from which only the highest peaks of the pre-existing reliefs emerged; this enormous inland “sea”, whose last remnant can be considered Lake Balaton, was gradually filled by river deposits, consisting of coarser deposits alternating with finer sediments of löss of wind transport, particularly abundant in the interglacial periods. Approximately 70% of the Hungarian territory is in any case formed by plains and the remainder by modest undulations (only 2% exceeds 400 m above sea level and no peaks exceed 1015 m); however, including the first Carpathian elevations as well as some isolated reliefs, such as the Selva Baconia, closely linked to the Alpine system, various morphologically and structurally well differentiated regions can be distinguished in the country.
According to itypeusa, the first fundamental division distinguishes: to the west the Transdanubia (Dunántúl) to the west of the Danube, which is the basic dividing element of Hungarian geography; a E the Great Plain or Lower Hungarian Plain (Nagyalföld or more simply and commonly Alföld, low land) east of the river; to the N a narrow mountainous area, made up of the pre-Carpathian reliefs enclosed between the Danube and the Tisza. The Transdanube, which extends between the Danube, the Drava and the eastern offshoots of the Alpine system, actually includes very varied subregions: the Kisalföld or Little Alföld (or Upper Hungarian Plain), to the N, of which Hungary has only the southern section (the northern one is included in the Slovak Republic), in the center the Selva Baconia, finally to the S the southern Transdanubian section. In the Kisalföld the courses of the Danube and its tributary Rába they enclose a marshy area still not fully drained (and therefore still not fully exploited for agriculture); in the most depressed part there is the lake of Fertö (Neusiedl), Hungarian only in the last southern part, while almost all of it is Austrian. However, in the western extremity of Kisalföld, near the border with Austria, the terrain becomes more raised, more rugged, due to the presence of the last foothills of the Alps: the massifs of Sopron and Köszeg, even if of modest altitude, dominate a belt of low hills. The Selva Baconia (the Bakony) is a complex of reliefs formed at the same time as the Alps and to the Carpathians, between which it forms a kind of link; broken by fractures partly filled by more recent deposits, the Bakony (704 m in Mount Körishegy) has a very varied morphology, with deep valleys, undulating plateaus, frequent karst phenomena for the limestone rocks, alongside, however, granite outcrops and basaltic flows; the original forest, from which the area was named, has been extensively cleared to give life to agricultural and industrial centers in the valley bottoms. The Bakony to the NE continues the groups of Vértes, Gerecse, Pilis and the hills of Buda, overlooking the capital.
The southern Transdanubian section, which extends to the S of the Balaton, is more monotonous, although it includes in addition to a vast platform of löss various hills, from which emerges the limestone massif of Mecsek (682 m). The Alföld, which corresponds to the main section of the ancient Pannonian basin, covers half of the Hungarian territory. It includes the interfluvial area between the Danube and the Tisza (the so-called Hungarian Mesopotamia) and that to the E of the Tisza or Transtibisco (Tiszántúl), crossing morphologically and structurally the Hungarian-Romanian borders, until reaching the first heights of Transylvania. Not even the Great Plain is uniform, especially for the structure of the soil, in the highest points made up of löss plateaus and sandy ridges while in the most depressed ones by floodable areas or even marshy basins. Alföld is undergoing transformation, while remaining there puszta from vast horizons its dominant note; reforestation, irrigation works, the introduction of new crops tend to make this region one of the largest agricultural areas in Europe. The third fundamental Hungarian region, the Felföld (high ground), appears quite different in the northern margin, as opposed to the underlying Alföld. These are hills that can be considered structurally precarpatic and which constitute the highest area of the country. These reliefs were subject, as indeed the inner belt of the Carpathians, to intense phenomena of volcanism, leaving clearly visible traces of imposing flows. Each massif has characteristics that differentiate it from the others. The Börzsöny rises from W(939 m), in which andesitic flows interpose themselves between layers of sandstone; after the more modest group of Cserhát rises the massif of the Mátra Mountains which, although similar in formation to Börzsöny, due to the greater altitude (here is the highest Hungarian peak, Mount Kékes, of 1015 m) has suffered the most from the effect of the periglacial processes, from which cracks in the ground and simultaneous rounding of the tops; finally follows the limestone group of the Bükk Mountains (959 m). The extension of the so-called Slovak Karst also belongs to the northern region, with the famous stalactite caves of Baradlawhich, 22 km long, are located for 2/3 in Hungarian territory, and the heights of Hegyalja, whose soil, due to its volcanic origin, due to its exposure at noon and being sheltered from the cold northern winds, lends itself very well to viticulture, producing the famous tokaj.