Elan valley reservoir and dam

The Craig Goch Dam, often called the Top dam, is a masonry dam in the Elan Valley of Wales and creates the upper-most of the Elan Valley Reservoirs. Construction on the dam began in 1897, and it was completed in 1904. The primary purpose of the dam and the other reservoirs is to supply Birmingham with water.

Wales (Welsh: Cymru [ˈkəm.rɨ] (listen)) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in 2021 of 3,107,500 and has a total area of 20,779 km2 (8,023 sq mi).

The Principality of Wales (Welsh: Tywysogaeth Cymru) was originally the territory of the native Welsh princes of the House of Aberffraw from 1216 to 1283, encompassing two-thirds of modern Wales during its height of 1267–1277. Following the conquest of Wales by Edward I of England of 1277 to 1283, those parts of Wales retained under the direct control of the English crown, principally in the north and west of the country, were re-constituted as a new Principality of Wales and ruled either by the monarch or the monarch's heir though not formally incorporated into the Kingdom of England.

The Elan Valley (Welsh: Cwm Elan) is a river valley situated to the west of Rhayader, in Powys, Wales, sometimes known as the "Welsh Lake District". It covers 70 square miles (180 km2) of lake and countryside.The valley contains the Elan Valley Reservoirs and Elan Village, designed by architect Herbert Tudor Buckland as part of the same scheme.