Since the sun is declining toward the hills, I would suggest that direction.

The sun was declining, shadows were growing longer.

Later, as the sun declined towards the western desert, he walked down to the temple.

The sun had declined almost to the horizon, growing bloated and red as it touched the distant earth.

The sun was declining as they came back through the wood.

Behind them, the sun was declining in the sky.

The sun declined, illuminating the eastern wall of the gulch.

The sun had declined from noon when he woke, smiling into her eyes, and stretched like a cat.

They found themselves on a marshy margin between lake and the dark hills, upon which the sun was declining.

Behind the mountains, the sun declined from the Land, and their shadows filled the air with omens.