Rubacava is amazing^
On the docks at night, with the changing music at each locale. The lighthouse, the mortuary, the central area...
Another love of mine are the hand-painted backgrounds in KQV and VI. For example, the Dark Forest in V, and the crossing with the Nightingale in VI. The music is really serene at the Nightingale, which adds beauty to the scene.
I am intrigued by Riven but don't own the game. I would play it just for the fascinating locales.