The Caspian — Gates

Ancient writers like Pliny described it as a narrow, scorched-looking passage with salt water leaching from the rocks, a description that still matches the modern site's barren, eroded appearance. CASPIAN GATES - Encyclopaedia Iranica

This pass was famously used by Alexander the Great in 330 B.C. during his pursuit of the Achaemenid king Darius III. The Caspian Gates

In the strictest historical sense used by Greco-Roman authors, the Caspian Gates (ancient Caspias portas ) refer to a ground-level pass through the in modern-day Iran. Ancient writers like Pliny described it as a

Identified with the Tang-e Sar-e Darreh , located roughly 50 miles (82 km) east of the ancient city of Rhagae (modern Ray, south of Tehran). south of Tehran).