The official Pokémon movie blog has updated. Translations of the new entry follows:
Appear! Movie Details #4: "Désser Tower" Concept Art Appears!
The story is set in "Désser City", a city located in the middle of a desert.
In the outskirts of the city stands "Désser Tower", a tower closely related to mythical Pokémon!
Source:
http://www.pokemon-movie.jp/pokemovie_ch/?p=398