The Cave of Sleep (from Metamorphoses XI)
Think of it like this:

There's a green hillside, a twilight sky. A grove of poppies is growing like a beard on the landscape, down by a pool. Dark blue, stars, a clear night. A stream is quietly bubbling across the landscape, and runs through the pool. It's the only sound.

Into this walks Iris. When she moves, she leaves behind a rainbow trail of images of herself. She stops in front of the pool, and her ghosts merge into herself to make her radiant.

She leaps, headfirst, into the pool, splitting again, and the camera follows her under the dark water.

There's a cave mouth on one wall of the pool; after the obligatory swimming bit she finds it and swims through it and up. Her curving path (followed by the camera) meets the top of the water, but she keeps swimming, and leaves the water vertically. Instead, she is now swimming through dreams. Some are light, some are dark, and the effect is rather like that escher drawing with the tesselating swans. But it's in 3D and the dreams are squirming and morphing and Iris swims through them, not just shoving them out the way as Ovid suggests. A sussuration on the edge of hearing. A whispering. The dreams meet again behind her rainbow, like a fluid, like amoebas. The roof is vaulted, a cathedral to all things somnolescent. A lighting effect is evident around her. The roof and the walls are blue-tinted and a long way off.

Eventually she reaches the end, and slides out into the main cavern. The roof is again vaulted, peaking in a dome far above. Various young men are seated on wooden intricately carved seats on the edges of the room; all have long hair which is strewn over their faces. Each chair is carved differently. Some have abstract patterns, some have birds, some have stones.

In the centre of the room is an ebony couch, with a dark blue throw over it. It has constellations sewn into its pattern with stitches not of yellow thread but of fire. It hovers about eight feet off the ground, with no visible means of support. Iris walks into the room, and her sphere of light, shed onto the walls, begins to disturb the young men, who begin to stir in their sleep. She looks at the couch, shrugs, and without apparent effort rises to meet it.

There's a large man lying on it. He's fairly chunky in build, and his head is pillowed on his arms which are in turn resting on the pillows. As Iris rises, her sphere of light rises with her, and falls on him. Once, twice, thrice, his head rises and eyes half-open; but always he falls back, until finally with a seeming-great effort he props his head upon his arm. His eyes open, and he mouths the words "Why have you come?"

Iris delivers the speech that Ovid has given her. Circumlocution and litany. Somnus looks more and more tired as she goes on, until finally she has finishes. Her radiance has noticeably dimmed by now, and she yawns, looks alarmed, returns to ground level, and more or less runs out of the room.

Somnus himself looks around, and finally his eyes light on one young man who sits in a chair carved with anthropomorphic yet almost abstract patterns. His face is not visible. When Sleep's glance falls upon him his head rises; and he has no face, just a smooth visage. While his head rises, his features begin to crawl, first eyes appearing, then a nose, until his face is complete. Sleep makes a languid gesture with his arm, then slumps back.

The young man, Morpheus, shrugs, and a pair of wings with dark semitransparent feathers emerge from his back. He walks out; there is a distant resumation of the whisperings on the edge of hearing as he enters the dreams; but these soon die.

Silence returns to the dark-blue lit cavern.