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"A projecting watchtower, or other advanced work, before the gate of a castle or fortified town. The term Barbican was more specially applied to the outwork intended to defend the drawbridge, which in moden fortifications is called the tete du pont." — Chambers' Encyclopedia, 1875

Barbican

"A projecting watchtower, or other advanced work, before the gate of a castle or fortified town. The…

"Gate-tower or Barbican, Walmgate Bar, York, England. In medieval fortification, a tower built beside or over a gate, as of a city, etc., for the purpose of defending the passage." -Whitney, 1911

Barbican of Walmgate Bar

"Gate-tower or Barbican, Walmgate Bar, York, England. In medieval fortification, a tower built beside…