arremolinar

To make something swirl or eddy — water, dust, leaves — and, almost as commonly, used reflexively for a crowd bunching up and milling around a point: la gente se arremolinó en la entrada. It's the verb behind torbellino (whirlwind) and remolino (eddy/whirl).

• Las hojas se arremolinaban en la esquina. — The leaves were swirling around on the corner.
• La multitud se arremolinó frente al escenario. — The crowd bunched up in front of the stage.
• El viento arremolinaba el polvo del camino. — The wind swirled the dust on the road.

Using arremolinar for a simple, orderly gathering — it specifically evokes a swirling, somewhat chaotic clustering (of people, wind, water, dust), not a calm queue or line.