Ulai
The Ulai is the river beside which Daniel receives the vision of the ram and the goat. Both notices fall in a single chapter and locate the visionary scene in the province of Elam.
The River by Shushan
The setting is given as Daniel begins to recount the vision. "And I saw in the vision; now it was so, that when I saw, I was in Shushan the palace, which is in the province of Elam; and I saw in the vision, and I was by the river Ulai" (Dan 8:2). The river fixes the vision to a real place — Shushan, in Elam — and Daniel is positioned beside it for what follows.
Where the Voice Calls Gabriel
The river returns when the interpreting angel is summoned. "And I heard man's voice between [the banks of] the Ulai, which called, and said, Gabriel, make this man to understand the vision" (Dan 8:16). The voice issues from over the river itself; the bracketed insertion "the banks of" makes explicit that the call comes from between Ulai's two sides. The river is thus more than a setting: it is the geographic axis along which the heavenly voice and the angel Gabriel converge to interpret the vision to Daniel.