A barbican (from Old French: barbacane) is a fortified outpost or gateway, such as at an outer defense perimeter of a city or castle, or any tower situated over a gate or bridge which was used for defensive purposes.
In the Middle Ages, barbicans were typically situated outside the main line of defenses, and were connected to the city walls with a walled road called the neck. In the 15th century, with the improvement in siege tactics and artillery, barbicans lost their significance. However, several barbicans were built well into the 16th century.
Fortified or mock-fortified gatehouses remained a feature of ambitious French and English residences well into the 17th century.
Fortifications in East Asia also feature similar high structures. In particular, gates in Chinese city walls were often defended by an additional "archery tower" in front of the main gatehouse, with the two towers connected by walls extending out from the main fortification. Literally called "jar walls", they are often referred to as "barbicans" in English.