You should go to http://www.rodluc.com/ The art of Luca Rodolfi. Visit his freestuff, scroll down and download the abby ruin. Download the obj version and load it with textures. Copy and paste a version with the bryce default gray texture applied and look at the two side by side.

Basically, Modeling only buys you something in a scene if you can get the camera in a position where you can see the edges. Everything else in a ruin can be done by textures or making sure edges don't parallel. Abby Ruin  is an excellent example of putting detail only where it's needed.