Wales is the largest of the peninsulas on the western side of Britain. It consists of a complex of worn down mountain ranges, representing high plateaux. They are called the Cambrian Mountains. The highest and most glaciated area occurs in the north, especially around Snowdon (1,085 m), and often the mountains approach close to the sea.

The Cambrians largely comprise the upland areas, generally and collectively described as the Welsh Massif. In the south the massif includes an important coal-field, on which an industrial area has grown. It is the most densely populated part of Wales, with some two-thirds of the total population of 2.8 million inhabiting about one-eighth of the area. Two relief divisions may be distinguished in South Wales: a coastal plain which in the south-eastern part around Cardiff becomes up to 16 km wide, and the upland areas of the coalfield proper, which rise between 245 and 380 metres. In recent years the region has experienced very acute problems with the decline in the coal industry and high unemployment rates.

Much of the remainder of Wales consists of bare rock, barren moorland and rough pasture, with only a few people to the square kilometre. But this region constitutes the heartland of Wales, for centered upon the massif is the Welsh culture where the traditions and language of a Celtic people are best preserved.

In the upland areas sheep are the basis of the rural economy, and in the low-lying parts near the coast and in the valley bottoms dairy farming predominates.