A very interesting group of large gulls around Varna- attracted to the hot springs on the sea front and also there is a tip nearby with bathing pools.
Highlight was a possible Heuglin's. http://peteralfrey.blogspot.com/2010/12/hueglins.html A large long-winged and slate-grey mantled 3rd/4th winter gull which out here is as likely (or more likely) to be Heuglins as graellsii.
Also a fascinating assortment of Yellow-legged and Caspian Gulls with a bewildering array of variation. I have attempted to classify them into:
a) 'Good Caspians' : http://peteralfrey.blogspot.com/2010/12/caspian-gull.html
b) 'Good Yellow-legged Gulls: http://peteralfrey.blogspot.com/2010/12/yellow-legged-gull.html
c) 'Unassignable Variants/hybrids': http://peteralfrey.blogspot.com/2010/12/only-god-knows.html
Also here is a great link to more Caspo's in eastern Europe including lots more photos from Dimiter Georgiev (from Neophron Tours) and Gabriel Martin taken at Varna earlier this year :