That looks like a place a tired and worn out foxaroo would enjoy resting with a picnic. :)

The stonework looks excellent and I particularly like the gold circles in the ground of the gazebo and those around the lamps. As this is a WIP I'm presuming you're going to add more to this, or tweak the textures?

There are a few materials I like in this scene, the gold, the paving stones, and the alabaster in particular.

The other kinds of stonework, the columns, and especially the dirt all need extra work.

I'm rather disappointed that the columns turned out so flat and boring in the light of day.
They looked far more interesting at night...

I think that's because with the night time version there's variations in the amount of light hitting the columns, but you'd be aware of that already.

I can't see any shadows in the current scene. Which direction in relation to the gazebo is the light source?

If the sunlight can't be adjusted then would it be feasible to alter the texture of the columns to make them slightly darker in the appropriate places to simulate shadowing?

Technically, the light is coming from the entire sky, and isn't coming from a particular direction.
I cheated a bit, there's a texture you can use that simulates a sky, given a 3D angle that the sun would be at, and I just piped that into the sky lighting calculations.

I'd like to find a way to translate that input angle into an indication of where the light should come from, but right now I don't have any ideas.
Okay, maybe one idea, but it'll take a while to explore.