The Aupapātika Sūtra

What it gives instead: Mahāvīra arriving at the Pūrṇabhadra caitya outside Campā, King Kūṇika's procession going out to meet him, a forest grove, an aśoka tree, and a stone slab beneath it.

And a count — surrounded by fourteen thousand śramaṇas and thirty-six thousand śramaṇīs. Those are the monks and the nuns of the twelve companies, already enumerated, before there is anywhere for them to sit.

No ramparts. No gates. No tiered assemblies. In this layer samavasaraṇa names the gathering itself, not a place.