A barbican is a fortified outpost or gateway, such as an outer defense to a city or castle, or any tower situated over a gate or bridge which was used for defensive purposes. Usually barbicans were situated outside the main line of defences and 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 even in the 16th century.