The image shows the city center, however....
Red circle: availability_mask:[bitmask(TOWNZONE_OUTSKIRT, TOWNZONE_OUTER_SUBURB), ALL_CLIMATES | bitmask(ABOVE_SNOWLINE)];
Blue circle: availability_mask: [bitmask(TOWNZONE_INNER_SUBURB), bitmask(CLIMATE_TEMPERATE, CLIMATE_ARCTIC, ABOVE_SNOWLINE, CLIMATE_TROPICAL)];
Yelow circle: availability_mask: [bitmask(TOWNZONE_OUTER_SUBURB, TOWNZONE_OUTSKIRT), bitmask(CLIMATE_TEMPERATE, CLIMATE_ARCTIC, ABOVE_SNOWLINE, CLIMATE_TROPICAL)];
Assuming the zones don't work in the editor ... other example: A Skycraper far from center... this time not in the editor, it´s ingame.... availability_mask:[bitmask(TOWNZONE_CENTRE), ALL_CLIMATES | bitmask(ABOVE_SNOWLINE)];