You can find mono-culture in both cities and rural areas. In cities there are more options, but in rural areas you can really get into it. In cities you can select from several different mono-cultures and ignore all others. In rural areas you can really get deep though because a commune can ensure you never encounter anything else, while in cities you still see them on the streets you just don't interact (though my experience is communes have outsiders come in for various supplies from time to time). If you don't live in a commune though rural areas don't provide choice - your neighbor is the only option no matter how strange they are.