You can find one of my most recent tutorials in the current issue of 3DArtist magazine, which is out now. The article takes you through creating a fantasy castle built on a forest covered mountain in Blender. Here’s a link to the newspost on Issue 74, where you can see what else is in store for that issue as well. You can buy a copy on the Imagine Publishing Store.
Here’s a look at the final product:
BenSimonds.com 
what could be a easy way to model the base mesh of the bridges? (step 4 in the magazine tutorial) thanks 🙂
Try starting with a circle for the underside of the arch. Then just delete the bottom half and extrude down for the pillars, up for the top of the bridge.