Fortifications of Derbent — Wikipedia

The Fortifications of Derbent (Darband) are one of the fortified defense lines, some of which date to the times as early as those built by the Persian Sasanian Empire to protect the eastern passage of the Caucasus Mountains (the "Caspian Gates") against the attacks of the nomadic peoples of the Pontic–Caspian steppe. With the first parts built in the 6th century during the reign of Persian Emperor Khosrow I and maintained by various later Arab, Turkish and Persian regimes, the fortifications comprise three distinct elements: the citadel of Naryn-Kala at Derbent, the twin long walls...