The: Caspian Gates

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

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 The Caspian Gates

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). This pass was famously used by Alexander the Great in 330 B