Re "Thomas Mann"
A possible third would be Venice ("Death in Venice"). But
a. Is the "connection" to Venice close enough (I don't know enough about Mann's "real" as opposed to fictional connections to the place)?
b. We already have Lubeck/Mann under books by Nobel Prize winning authorsRe "Labour Camp"
Robben Island had its quarry - does that make it a Labour camp as well as a prison? But wouldn't it be better just to add the Curonian Spit to Prisons because of the historic event cited? Most prisons involve some "labour" - indeed the connection between prison and labour camp is somewhat closer, I would have thought, than between labour and extermination camps? Re Artist Colonies
Taos certainly was a very significant "artist colony" and attracted notable "names" in the first half of 20C. I believe it still is - but perhaps less significant.
I fear that "arty" San Miguel Allende would also count - but possbily more for its Siqueiros etc roots than the hordes of "art course" tourists getting their Bachelors of Visual Arts and Masters of Fine Arts degrees!
There is a "definitional issue" also - what constitutes ans "artist colony". To me it means that a reaosnable number live there all year round. However it also seems to be used where there are annual "get togethers" perhaps based on the fact that 1 or 2 artists live there year round e.g.
Ohrid - http://en.wikipedia.org/wiki/Colony_Ramazzoti
Portobelo Panama - http://www.spelman.edu/artcolony/portobelo.html