Top five cities in Demographics.

[Harrier UK]

Also the thing to remember is - you get no culture by capturing Wonders - only their base benifit - if not obsolete.

[zeace]

It's not only culture though. You can use the victory status screen to see your opponents 3 most cultured cities. I've had many times when my 3rd culture city was much higher than their first, but still didn't make the top 5 cities list.