DOC area in the north-east of Portugal on the border with Spain. The name Trás-os-Montes means "Behind the mountains", as it is enclosed by high mountains in the west, which separate it from the rest of Portugal. It is the result of a division of the former country wine area of the same name (Vinho Regional), by merging the three former IPR areas of Chaves (west), Planalto-Mirandês (east) and Valpaços (centre). The southern part was separated off, classified as the Duriense Country Wine Area and assigned to the Douro Port Wine Area. The wines in the area that do not meet the DOC regulations can be marketed as Vinho Regional Transmontano. Due to the extreme climatic conditions (very hot and dry) and the predominant shallow granite soils, viticulture is very difficult.