For the CityZen-specific megacity and hot spot regions the following lon/lat ranges are suggested:

BeNeLux small (incl. BeNeLux and Ruhr area):
02 deg 30 min E - 08 deg 00 min E
49 deg 20 min N - 53 deg 40 min N

BeNeLux big (incl. BeNeLux small, London and Paris):
01 deg 00 min W - 08 deg 00 min E
48 deg 00 min N - 54 deg 00 min N

Po Valley small (incl. Milano, Turino, Genova):
07 deg 30 min E - 10 deg 30 min E
44 deg 00 min N - 46 deg 00 min N

Po Valley big (incl. Po Valley small, and area to the Adriatic):
07 deg 30 min E - 13 deg 30 min E
44 deg 00 min N - 46 deg 00 min N

Eastern Mediterranean:
22 deg 30 min E - 32 deg 30 min E
29 deg 00 min N - 42 deg 00 min N

Athens:
23 deg 00 min E - 25 deg 00 min E
37 deg 00 min N - 39 deg 00 min N

Cairo:
30 deg 00 min E - 32 deg 30 min E
29 deg 00 min N - 31 deg 00 min N

Istanbul:
28 deg 00 min E - 30 deg 30 min E
40 deg 00 min N - 42 deg 00 min N

Pearl River Delta:
112 deg 00 min E - 115 deg 30 min E
21 deg 30 min N - 24 deg 00 min N

For more general terms, e.g. “Eastern Europe”, the definitions of IPCC/IMAGE should be used. The netCDF and EXCEL files containing these definitions were kindly provided by Angelika Heil (FZJ) and can be accessed here.