As a result, conventional military strategies often demand possession of high ground. They may also conceal forces behind them, allowing a force to lie in wait on the crest of a hill, using that crest for cover, and firing on unsuspecting attackers as they broach the hilltop. Hills provide a major advantage to an army, giving them an elevated firing position and forcing an opposing army to charge uphill to attack a fort or other position.
The National Cathedral in Washington, DC has followed this tradition and was built on the highest hill in that city. In Britain, many churches at the tops of hills are thought to have been built on the sites of earlier pagan holy places. Some of these are defensive structures (such as the hill-forts of the Iron Age), but others appear to have hardly any significance. In northern Europe, many ancient monuments are sited in heaps. Some settlements, particularly in the Middle East, are located on artificial hills consisting of debris (particularly mud bricks) that has accumulated over many generations. For example, Ancient Rome was built on seven hills, helping to protect it from invaders. Many settlements were originally built on hills, either to avoid floods (particularly if they were near a large body of water), or for defense (since they offer a good view of the surrounding land and require would-be attackers to fight uphill), or to avoid densely forested areas. Pingo – a mound of earth-covered ice found in the Arctic and Antarctica.Puy – used especially in the Auvergne, France, to describe a conical volcanic hill.Tor – a rock formation found on a hilltop also used to refer to the hill, especially in South West England and the Peak District.Kuppe – a rounded hill or low mountain, typical of central Europe.Butte – an isolated hill with steep sides and a small flat top, formed by weathering.Drumlin – an elongated whale-shaped hill formed by glacial action.Brae – Scots, Ulster, and North of England term for a hillside or brow of a hill.Many such names originated in one geographical region to describe a type of hill formation peculiar to that region, though the names are often adopted by geologists and used in a wider geographical context. Various names may be used to describe types of hills, based on appearance and method of formation. The rounded peaks of hills results from the diffusive movement of soil and regolith covering the hill, a process known as downhill creep. Hills may form through geomorphic phenomena: faulting, erosion of larger landforms such as mountains and movement and deposition of sediment by glaciers (notably moraines and drumlins or by erosion exposing solid rock which then weathers down into a hill).
In Wales, the distinction is more a term of land use and appearance and has nothing to do with height. In practice, mountains in Scotland are frequently referred to as "hills" no matter what their height, as reflected in names such as the Cuillin Hills and the Torridon Hills. Some definitions include a topographical prominence requirement, typically 100 feet (30.5 m) or 500 feet (152.4 m). In contrast, hillwalkers have tended to regard mountains as peaks 2,000 feet (610 m) above sea level: the Oxford English Dictionary also suggests a limit of 2,000 feet (610 m) and Whittow states "Some authorities regard eminences above 600 m (1,969 ft) as mountains, those below being referred to as hills." Today, a mountain is usually defined in the UK and Ireland as any summit at least 2,000 feet or 610 meters high, while the official UK government's definition of a mountain is a summit of 600 meters (1,969 feet) or higher. Geographers historically regarded mountains as hills greater than 1,000 feet (304.8 meters) above sea level, which formed the basis of the plot of the 1995 film The Englishman Who Went Up a Hill But Came Down a Mountain. The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally considered to be not as tall, or as steep as a mountain.