Like the rest of the chain, the island is sharply mountainous. It has an area of 278 km².
Nicknamed Isla Meridiana ("the meridian island", see below), it is part of the province of Santa Cruz de Tenerife. It is divided into two municipalities, Valverde in the northeast and Frontera in the southwest, both of which contain several villages. The seat of the island government (cabildo insular) is in Valverde town. 10 002 people (2002) live on the island.
Like all the Canary Islands, El Hierro is a tourist destination. It is served by a small airport at Valverde and a ferry terminal, both of which connect to Tenerife.
The island's name in several languages (including French, German, Danish) is Ferro, known in history as the prime meridian in common use outside of the British Commonwealth. Already in the 2nd century A.D., Ptolemy considered a definition of the zero meridian based on the western-most position of the world, giving maps with only positive (eastern) longitudes. In the year 1634, France ruled by Louis XIII and Richelieu decided that Ferro's meridian should be used as the reference on maps, since this island is the most western position of the Old World and also thought to be exactly 20 degrees west of Paris, so indeed the exact position of Ferro was never considered. Old maps (outside of Anglo-America) often have a common grid with Paris degrees at the top and Ferro degrees offset by 20 at the bottom. It was later found that the island of Ferro is indeed 20° 23' 9" west of Paris, but the Ferro meridian was still defined as 20 degrees west of Paris. -- See also prime meridian.