Deity
Śrī Kṛṣṇa
Part of Goloka
Not one form among several
The chart's whole vertical axis, every realm below this one, ultimately answers to a single claim about who sits at this exact point. Not one form of God among several, the tradition says — Svayaṁ Bhagavān, the original Supreme Person, the very source the other forms expand from.
Person, not portrait
So the chart's center isn't a portrait hung in a frame. It's the innermost point of a world built entirely out of relationship, and everything else on this chart is, in some sense, describing what surrounds Him.
Central whorl of the thousand-petalled Goloka lotus
Every other realm on this chart — Vaikuṇṭha's majesty, Maheśa-'s threshold, the material universes — is described here as radiating outward from this one point. Fixing Kṛṣṇa's position at the center first is what makes every other realm's position make sense.
Source: Brahma-saṁhitā 5.1–5; Gauḍīya theological explanation · Direct scriptural supportThe rest of the chart gets very detailed, but its basic point is simple: everything is arranged around a personal relationship with Kṛṣṇa.