Bala Hissar — "High Fort" in Dari — is the great citadel mound that anchors the northern edge of old Balkh. It is not a single building but a tells: a mound of compacted rubble and earth that represents 3,500 years of continuous occupation, each civilization building on the ruins of the last. Walking across it, you are stepping on layers of Achaemenid, Macedonian, Kushan, Arab, Timurid, and Uzbek occupation, though there is nothing clearly defined to see above ground.
The walls that enclose the old city, stretching for kilometres, are the other great survival of ancient Balkh. Made of mud brick, they have eroded to low ridges in many places, but in others they still stand several metres high. The circuit of walls represents one of the largest urban enclosures in Central Asia — the city that Genghis Khan destroyed in 1221 was enormous, and the walls give a sense of its scale. Both Bala Hissar and the walls are freely accessible, and the elevated position of the citadel offers views across the entire site.