Medieval fortification in the context of "River Monnow"

Castillo San Felipe del Morro (English: Promontory Castle of Saint Philip), most commonly known as El Morro (The Promontory), is a large fortress and citadel in the Old San Juan historic quarter of San Juan, the capital municipality of Puerto Rico. Commissioned by King Charles I of Spain in 1539, it was first built as a fortified tower in honor of King Philip II, who oversaw its expansion into a hornwork bastion fort by 1595. Over the next 200 years, especially in the reign of King Charles III, El Morro continued to be developed to reach its current form in 1787. Rising 43 metres (140 ft) from the Atlantic shoreline with 5.5 to 7.6 metres (18 to 25 ft) thick walls, the six-leveled edifice stands on a steep, rocky headland promontory on San Juan Islet guarding the entry to San Juan Bay, the harbor of Old San Juan. El Morro, alongside La Fortaleza, San Cristóbal, El Cañuelo, and other forts part of the Walls of Old San Juan, protected strategically and militarily important Puerto Rico, or La Llave de las Indias (The Key to the Indies), from invasion by competing world powers during the Age of Discovery and Sail. It was designated a World Heritage Site by UNESCO in 1983.

Castillo San Cristóbal (English: Saint Christopher Castle) is a fortress in the Old San Juan historic quarter of San Juan, the capital municipality of Puerto Rico, known for being the largest fortification built by the Spanish in the New World. Dating back to defense expansions following attacks by the English in 1598 and Dutch in 1625, it was first constructed in 1634 as the Caballero de San Miguel (Saint Michael Cavalier) and the Garita del Diablo ("devil’s sentry box"). Over the next 150 years, especially in the reign of King Charles III of Spain, it continued to be developed into a bastion fort with outer ravelins and batteries to reach its largest size in 1783. Rising 150 ft from the Atlantic shoreline, the three-level edifice stands on a hill at the northern coastline of San Juan Islet, guarding the land entry to Old San Juan. Alongside El Morro, La Fortaleza, and other forts part of the Walls of Old San Juan, it protected strategically and militarily important Puerto Rico, or La Llave de las Indias (The Key to the Indies), from invasion by competing world powers during the Age of Sail. It was designated a World Heritage Site by UNESCO in 1983.

La Fortaleza (English: "the fortress"), officially the Palacio de Santa Catalina ("Saint Catherine's Palace"), is the official residence and workplace of the governor of Puerto Rico. Located in the historic quarter of Old San Juan in the capital municipality of San Juan, it has served as the governor’s residence since the 16th century, making it the oldest executive mansion in continuous use in the New World. Built as a medieval fortress from 1533 to 1540 by orders of King Charles I of Spain, and remodeled to its present Neoclassical style in 1846 by orders of Governor Rafael Arístegui y Vélez, it was the first fortification erected by the Spanish on San Juan Islet to defend San Juan Bay, the harbor of Old San Juan. Alongside El Morro, San Cristóbal, and other forts part of the Walls of Old San Juan, it protected strategically and militarily important Puerto Rico, or La Llave de las Indias (The Key to the Indies), from invasion by competing world powers and harassment by privateers and pirates during the Age of Discovery and Sail. It was designated a World Heritage Site in 1983.

Situated in the western end of San Juan Islet in the Old San Juan historic quarter, La Fortaleza, seat of the executive branch, is about 1 mile (1.6 km) from the Capitol of Puerto Rico, seat of the legislative branch, in the center of the Islet in the Puerta de Tierra historic district, and 2 miles (3.2 km) from the Supreme Court Building, seat of the judicial branch, in the eastern end of the Islet in Puerta de Tierra.

A portcullis (from Old French porte coleice 'sliding gate') is a heavy, vertically closing gate typically found in medieval fortifications. It consists of a latticed grille made of wood and/or metal, which slides down grooves inset within each jamb of the gateway.

The Castle, Newcastle, or Newcastle Castle is a medieval fortification in Newcastle upon Tyne, England, built on the site of the fortress that gave the City of Newcastle its name. The most prominent remaining structures on the site are the Castle Keep (the castle's main fortified stone tower, pictured below right), and the Black Gate, its fortified gatehouse.

Use of the site for defensive purposes dates from Roman times, when it housed a fort and settlement called Pons Aelius (meaning 'bridge of (Publius) Aelius (Hadrianus)' - the Roman emperor Hadrian), guarding a bridge over the River Tyne. Robert Curthose, eldest son of William the Conqueror, in 1080 built a wooden motte-and-bailey-style castle on the site of the Roman fort. Curthose built this 'New Castle upon Tyne' after he returned south from a campaign against Malcolm III of Scotland. Henry II built the stone Castle Keep between 1172 and 1177 on the site of Curthose's castle. Henry III added the Black Gate between 1247 and 1250. Nothing remains above ground of the Roman fort or the original motte-and-bailey castle. The Keep is a Grade I listed building, and a scheduled monument.

Monnow Bridge (Welsh: Pont Trefynwy Welsh pronunciation: [pɔnt tre:vənʊɨ]), in Monmouth, Wales, is the only remaining fortified river bridge in Great Britain with its gate tower standing on the bridge. Such bridge towers were common across Europe from medieval times, but many were destroyed due to urban expansion, diminishing defensive requirements and the increasing demands of traffic and trade. The historical and architectural importance of the bridge and its rarity are reflected in its status as a scheduled monument and a Grade I listed building. The bridge crosses the River Monnow (Afon Mynwy) 500 metres (1,600 ft) above its confluence with the River Wye.

Monmouth had been a significant border settlement since the Roman occupation of Britain, when it was the site of the fort of Blestium. The River Wye may have been bridged at this time but the Monnow, being easily fordable, appears not to have had a crossing until after the Norman Conquest. According to the local tradition, construction of Monnow Bridge began in 1272 to replace a 12th-century Norman timber bridge. Through the medieval era, the English Civil War, and the Chartist uprising, the bridge played a significant, if ineffectual, role in defending Monmouth. It also served as a gaol, a munitions store, a lodge, an advertising hoarding, a focus for celebrations and, most significantly, as a toll gate. Much of the medieval development of Monmouth was funded by the taxes and tolls the borough was entitled to raise through royal charter. The tolls were collected through control of the points of entry to the town, including the gatehouse on Monnow Bridge.