Here's a very fast and simple HDR render I did with Vue 5 over a year ago. I used the stock Vim-HDR that comes with Vue- with a bluish tint as Cheers suggested. A spotlight on the statue (a bit too bright- but sort of realistic) suggests nighttime lighting. The IBL effect is best on the fountain water. I PERSONALLY would consider a mix of IBL and ray-traced lighting...

What I notice about nighttime lighting effects are the "vignette effect" on buildings, trees, etc. Basically they become somewhat "Cartoon-like".

Wikipedia:
In the visual arts, vignetting is a loss in clarity towards the corners and sides of an image (for example brightening, darkening, or blurring). The effect is sometimes used intentionally, for instance in photographic portraits. In photography (other than for these special effects) vignetting is usually unintentional, and is often caused by optical limitations of the lens. Clarity to the corners of a photograph is one of the features of high-end optics.