So the last time I ran a campaign of any length in D&D was with 3.5 edition rules and in the Eberron campaign setting. I started the group in Sharn which is the largest city on the main continent of Khorvaire. We played for several months before we ran out of steam, but I got the group up to 3rd level. We were in the Mournland when we stopped playing having just stymied the evil plans of the Emerald Claw.
I really like the 3.5 rule set, it is skill and feat heavy with great combat rules. The Eberron campaign setting came out about the same time as the 3rd edition rules and I really liked the gritty, steam-punk feel. It had some truly epic components as well as lots of wonderful small details.
The image in this post shows a great cross section of life in Sharn at an outdoor market place.