@ascanius - you need to make 5 posts first before you can link off-site content (kind of SPAM protection for the site.)

It would be hard to make the best suggestion for you, not knowing what software you are using. There are many ways to create a sense of height in terrain. For buildings its a bit more difficult, but hand created shadows is a great way to imply height in buildings. I don't mean drop shadows, though that can work for the immediate, but only if all buildins are the same height. Photoshop/GIMP lets you use bump maps to simulate height for terrain. I use stacked beveled shapes extensively to imply height. Again it depends on how you work, and what software you use.