Fort file

The fort file

Sourced facts about castles and fortifications, kind by kind. Every fact links to its source, checked 29 Oct 2026.

Hillforts

Hillfort building began throughout Britain over 2,600 years ago, in the Iron Age. [source]
Maiden Castle in Dorset is one of Europe’s largest Iron Age hillforts, covering an area bigger than 50 football pitches. [source]
At its peak, hundreds of people lived inside Maiden Castle, with over 100 roundhouses within its defences. [source]
Digs in the 1930s showed people were active on the Maiden Castle hilltop about 3,000 years before the first hillfort was built. [source]
Groups of four posts found inside hillforts are thought to be raised granaries, keeping grain dry and away from vermin. [source]

Brochs are a kind of Iron Age roundhouse found only in Scotland. [source]
Mousa Broch in Shetland is the tallest and best-preserved Iron Age tower in Scotland. It stands 13 metres tall and is thought to date from about 300 BC. [source]

Hadrian’s Wall was built on the orders of the Emperor Hadrian from about AD 122, at the northern edge of Roman Britain. [source]
Hadrian’s Wall was 118 km (73 miles) long, crossing northern Britain from coast to coast. [source]
As well as the Wall itself there was an earthwork, a ditch, two major roads and numerous forts, milecastles and turrets. [source]
Further north, the Antonine Wall in Scotland, about 60 km long, was started in AD 142. [source]
Hadrian’s Wall is part of the Frontiers of the Roman Empire World Heritage Site, first inscribed in 1987. [source]

A motte is a mound. A bailey is a yard around the foot of the mound, enclosed at first by wooden fences (palisades) and later by stone walls and towers. [source]
Motte-and-bailey castles spread throughout western Europe in the 11th century. [source]
The keep was the strongest part of a castle, where the whole garrison retreated in a siege once the outer defences had fallen. [source]

Edward I reigned from 1272 to 1307. [source]
Edward I’s castles at Caernarfon, Conwy, Beaumaris and Harlech are grouped together as a World Heritage Site, inscribed in 1986. [source]
At Caernarfon, Edward I and his military architect, Master James of St George, built a castle, town walls and a quay all at the same time. [source]
Beaumaris and Harlech combine 13th-century double walls (one ring of walls inside another) with a central plan. [source]
Caernarfon has polygonal (many-sided) towers, eagle statues and bands of different-coloured stone. [source]

Krak des Chevaliers in Syria was built by the Knights Hospitaller (the Order of St John) between 1142 and 1271. [source]
In 1271 it was captured by the Mamluk sultan Baybars I. [source]
With more building by the Mamluks in the late 13th century, it is among the best-preserved Crusader castles. It became a World Heritage Site in 2006. [source]

Gunpowder changed how forts were built. Angled, bastioned forts, called alla moderna, spread across Europe. [source]
The Republic of Venice built bastioned defences in the 16th and 17th centuries, now a World Heritage Site inscribed in 2017. [source]
Sébastien Le Prestre de Vauban (1633–1707) was a military engineer for King Louis XIV of France. His forts became a World Heritage Site in 2008. [source]
Vauban’s World Heritage forts include whole towns he built from scratch, as well as citadels and bastion walls. [source]

Himeji Castle in Japan is the finest surviving example of early 17th-century Japanese castle architecture. [source]
Himeji is a masterpiece of building in wood, with white plastered earthen walls and many layers of roof. [source]
Himeji is also called White Heron Castle. Its walls were covered in white, fireproof plaster. [source]
Himeji Castle became a World Heritage Site in 1993. [source]

Martello towers are named after Cape Mortella in Corsica, where British forces captured a round tower only with great difficulty in 1794. [source]
When Napoleon threatened to invade, 74 Martello towers were built on the most vulnerable stretch of England’s Channel coast. [source]
English Channel Martello towers were 9 to 12 metres high, with walls 3 metres thick on the seaward side. The door was reached by a 6-metre ladder. [source]
The Martello tower at Sandycove near Dublin, where James Joyce lived briefly in 1904, is now the James Joyce Tower & Museum. [source]

Castle Rushen in Castletown is one of the best-preserved medieval castles in the British Isles. [source]
Manx National Heritage says Castle Rushen was built 800 years ago for a Viking king, and has been a Civil War fortress and the Island’s Victorian prison. [source]
Castletown is the ancient capital of the Isle of Man. [source]
Peel Castle stands on St Patrick’s Isle. Inside a 700 m curtain wall are almost two hectares of fortifications built over 700 years, with a cathedral, a church, chapels and cemeteries. [source]

When	What happened
About 300 BC	Mousa Broch thought to be built [source]
About AD 122	Hadrian’s Wall begun [source]
AD 142	Antonine Wall started [source]
11th century	Motte-and-bailey castles spread across western Europe [source]
1142 to 1271	Krak des Chevaliers built by the Hospitallers [source]
1272 to 1307	Reign of Edward I [source]
16th and 17th centuries	Venice builds bastioned defences [source]
Early 17th century	Himeji Castle in its surviving form [source]
1633 to 1707	Life of Vauban [source]
1794	British capture the tower at Cape Mortella [source]
1803	Invasion threat from Napoleon; Martello towers follow [source]

Dates are as given by each source. “About” means the source gives an approximate date.

Opening times and prices change, so we don’t list them. Check the site’s own page before you go: Castle Rushen, Peel Castle, Caernarfon Castle, Maiden Castle, Mousa Broch.

For a visit, a project or a rainy afternoon: Hadrian’s Wall maps · Hadrian’s Wall Path guidebooks · Roman Britain books · Castle books for children · Castle model kits · Roman fort model kits. These are Amazon UK search links, not endorsements of particular products. As an Amazon Associate I earn from qualifying purchases.