Kecia Hansen has been slowly building up a library of virtual modules for a microscale castle
. This has gone through a couple of iterations, but her more recent redesign has about fifty 16x16 modules, with defined connections, roads, and walls:
She includes anything you can think of - walls, gates, towers, keeps, homes, churches, a port, attacking armies - and these can all be combined to make a huge walled city layout:
About half of these have been uploaded to the Design by Me section of Lego.com. Go to the gallery
and type lara34 into the username box and hit the green triangle (don't just hit your enter key - I kept doing that and it would say there were no matches, which was frustrating). You can download the LDD files and even purchase the modules in kit form.