I've looked and looked for something like this for a LONG time and found absolutely nothing... has anyone ever come across any worlds with a Greek or Roman type of theme?

here's a usefull thread:
http://modthesims.info/showthread.p...d=1#post4161332

I did see that thread, the first world looks interesting, but the second one was removed by Rapidshare and the creator never bothered to reupload it (I looked but was unable to find any place to download it). Such a shame, it does look like an excellent world.

how about this one:
http://www.thesims3.com/assetDetail...assetId=5246622

How much building can you do yourself?

There are cute mediterranean worlds - Nilxis has some to start with. You could use an Egyptian world like Al Shibalba too. If the world you like is too modern or has other problems and doesn't come with CAW files you can extract it from the sims3pack and edit it yourself. (CAW is mainly a pain for big redos or for sculpting and painting - moving things around is easy and it auto rebuilds routing and auto merges trees now on save so there's nothing to worry about. Something like stripping out all roads would be very easy.)

venusprincess100 already mentioned Ancient Roman Home by Yogi-Tea. Gissence's Roman Bath is beautiful too.

For building ideas, Nilxis again has some Roman-themed buildings in this new unpublished world. You can get a good sims version of a roman-style floorplan in a few of the pics which could be helpful for a house you can plop down everywhere. If you google "roman house plans" or "ancient greek house plans" you get a wealth of information and, luckily, they're mostly very square so they're not too hard to make in game

Finally if you don't specifically need it to be ancient you can use one of the 100s of medieval worlds and their 100s of medieval items and replace some buildings with the above and repaint the other buildings in town so that it's a medieval roman or greek town. That would be a lot easier but if it's not what you want it's no good for you.