July 30, AD 762

Round City of Baghdad

Al-Mansur begins building his new capital at Baghdad

Astrologers picked the hour to break ground — and modern scholarship still cannot agree whether the day was 30 July, 31 July or 2 August.

Breaking ground on the City of Peace

What is conventionally commemorated on 30 July 762 was not a caliph moving house. It was the ceremonial foundation, or commissioning, of a city that did not yet exist.

Al-Mansur, the second Abbasid caliph, sited his new administrative centre near where the Sarat canal system met the Tigris. He gave it the official name Madinat al-Salam, the City of Peace. Astrologers including Nawbakht and Umar ibn al-Farrukhan chose an auspicious moment to begin the work.

Which day, exactly, remains contested

The 30 July date is widely repeated but not settled. Published reconstructions also give 31 July 762 — one specifying about 1:57 in the afternoon — and 1 Jumada 145 AH, equivalent to 2 August 762.

Part of the spread comes from converting early Hijri dates; part from disagreement among the narrative traditions themselves. The foundation, the caliph's own relocation, the completion of the Round City and the transfer of the administrative departments occurred in separate stages.

What actually existed by nightfall

Nothing like a completed capital existed by nightfall. Construction on the palatial settlement later known as the Round City ran from roughly 762 to 766 or 767, and the palace, mosque and administrative buildings all needed time before the caliph could live among them.

Al-Mansur transferred his residence around 763 or 764, after the initial building work. The name Baghdad, meanwhile, was older than his city and belonged to the area before he arrived; it outlived the official City of Peace.

Sources

Researched 23 Aug 2026 7 sources 2 audit passes Date disputed

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date disputed. Sources disagree; the research places it at ~0762-07-30.

What the sources leave uncertain

30 July is a widely repeated traditional date, but scholarly reconstructions also give 31 July or 2 August 762. Conversion of early Hijri dates and disagreement among narrative traditions account for part of the variation.
The foundation, the caliph’s residential move, completion of the Round City, and transfer of all administrative departments were separate stages and should not share one date.
The area was already known as Baghdad before al-Mansur; what he founded was the Abbasid palatial and administrative city officially named Madinat al-Salam.