The ten-day autumn festival linked with the mahanavami dibba is known…

NCERT (2026-27): “4.1 The mahanavami dibba …
Located on one of the highest points in the city, the “mahanavami dibba” is a massive platform rising from a base of about 11,000 sq. ft to a height of 40 ft. There is evidence that it supported a wooden structure. The base of the platform is covered with relief carvings (Fig. 7.12).”

“Rituals associated with the structure probably coincided with Mahanavami (literally, the great ninth day) of the ten-day Hindu festival during the autumn months of September and October, known variously as Dusehra (northern India), Durga Puja (in Bengal)”