User blog comment:Jarcellon/Soul Farming Locations/@comment-1852943-20130403155906/@comment-5264386-20130403221351

Personally, I would recommend these minimum levels:
 * Blighttown Swamp: SL 40
 * Painted World: SL 45 ~ 50
 * New Londo: SL 60
 * Tomb of the Giants: SL 70