Yeah, it's the walls around the pool that really throw it off for me.  They're wider than your minarets, making everything else look itty bitty.

What I think really works with scale is deciding that one bryce unit is one inch, one foot, meter, yard, etc., then building everything to scale so you don't have one thing too big throwing everything else off.

Adding more detail to the buildings themselves wouldn't hurt either--windows or something decorative.  You might be able to get away with just using a texture for the details.