The ancient city of Balkh was known to the Ancient Greeks as Bactra, giving its name to Bactria. It was mostly known as the centre and capital of Bactria or Tokharistan. Marco Polo described Balkh as a "noble and great city". Balkh is now for the most part a mass of ruins, situated some 12 km (7.5 mi) from the right bank of the seasonally flowing Balkh River, at an elevation of about 365 m (1,198 ft).
French Buddhist Alexandra David-Néel associated Shambhala with Balkh, also offering the Persian Sham-i-Bala ("elevated candle") as an etymology of its name. In a similar vein, the Gurdjieffian J. G. Bennett published speculation that Shambalha was Shams-i-Balkh, a Bactrian sun temple.
The Bactrian language name of the city was βαχλο. The name of the province or country also appears in the Old Persian inscriptions (B.h.i 16; Dar Pers e.16; Nr. a.23) as Bāxtri, i.e. Bakhtri. It is written in the Avesta as Bāxδi. From this came the intermediate form Bāxli, Sanskrit Bahlīka (also Balhika) for "Bactrian", and by transposition the modern Persian Balx, i.e. Balkh, and Armenian Bahl.
Balkh is considered to be the first city to which the Indo-Iranian tribes moved from north of the Amu Darya, between 2000 and 1500 BC. The Arabs called it Umm Al-Belaad or Mother of Cities on account of its antiquity. The city was traditionally a center of Zoroastrianism. The name Zariaspa, which is either an alternate name for Balkh or a term for part of the city, may derive from the important Zoroastrian fire temple Azar-i-Asp. Balkh was regarded as the place where Zoroaster first preached his religion, as well as the place where he died.
Since the Indo-Iranians built their first kingdom in Balkh (Bactria, Daxia, Bukhdi) some scholars believe that it was from this area that different waves of Indo-Iranians spread to north-east Iran and Seistan region, where they, in part, became today's Persians, Tajiks, Pashtuns and Baluch people of the region. The changing climate has led to desertification since antiquity, when the region was very fertile. Its foundation is mythically ascribed to Keyumars, the first king of the world in Persian legend; and it is at least certain that, at a very early date, it was the rival of Ecbatana, Nineveh and Babylon.