barbacans

A barbican is a fortified outpost or gateway, typically to a castle or a town. It is usually a projecting part of a defensive structure, often a tower or a wall, that provides flanking fire or additional protection to an entrance. Barbicans were a common feature of medieval fortifications.

These structures could take various forms. Some were simple outworks designed to defend a main gate, consisting of a wall with battlements and perhaps a drawbridge. Others were more elaborate, with multiple layers of defense, including towers, walls, and ditches. The primary purpose of a barbican was to slow down or repel attackers attempting to breach the main defenses, especially at the vulnerable point of a gate. They allowed defenders to engage enemies at close range before they reached the main gate, and also provided a protected area from which to launch counter-attacks.

The design of barbicans evolved over time with changes in siege warfare. Early examples were often simple stone towers. As artillery became more significant, barbicans were adapted to withstand cannon fire, with thicker walls and more rounded shapes. The term "barbican" can also refer to a specific medieval fortification in London, England, which now serves as an art gallery. This London Barbican is a much later structure, built in the 20th century, and is not a historical military defense in the same sense as its medieval predecessors.