Samvasaran (Samavasaran) is the divine preaching hall that a Tirthankara creates after attaining kevala jnana. It is described as a grand, multi-layered circle where beings of all kinds can hear and see the teaching.

Three assemblies (three enclosures) in Samvasaran

• Structure: There are three concentric enclosures (gadhs). The outermost is silver, the middle is gold, and the innermost is studded with gems. This threefold setup helps accommodate different beings and stages of reception. The hall is centered under an Ashoka tree and has multiple entrances so beings from all sides can enter. ( jainqq.org)
• Viewing from all directions: The Tirthankara sits on a throne but is perceived by everyone as facing them. To ensure all listeners—humans, animals, and gods—can see and hear, three replicas of the Tirthankara facing the other three directions are created. This way, no matter where a listener sits, the sermon is accessible. ( jainqq.org)
• Seating of listeners: The listeners are arranged in order within the three halls so that beings of different types can attend. Common descriptions include:

- First hall: ascetics - Second hall: certain classes of divine beings (devas) - Third hall: aryikas (nuns) and laywomen - Additional halls: other groups of divine beings These arrangements reflect the Jain view of inclusive teaching to all sentient beings. ( jainqq.org)

In short:

• Samvasaran is a three-layered, jewel-decked celestial auditorium built after omniscience.
• It uses three directional replicas of the Tirthankara so every being can witness and listen.
• Listeners are seated in orderly halls according to their category, so the universal teaching reaches all beings.

You can read more about Samvasaran here