Why was Baghdad circular in ancient times?

The ancient Indian epic, the Ramayana, mentions a city located towards the West of India, after crossing a sea (Arabian) and a couple of mountain ranges. The city was circular "shaped like a wheel with a thousand (many) spokes". The city was made by a celestial architect by the name Vishvakarma. The name of the City was 'Chakra-van'.

The Ramayana describes the route from India right up to what is probably the Zagros range in Iran & Iraq.

Whether Baghdad was made on the ruins of the more ancient, way more ancient Chakravan is not known but there definitely was a perfectly circular city somewhere in the Zagros range as per the Ramayana. The 'Ramayana' is at least 7000 year old, if not older.