The entire set: ancient-medieval-industrial-modern 
These are the balcans of decadence. Try to run to the great church in the second series, or walk the stairs to the parthenon in the first, fall off the windows in the modern industrial set only to find yourself walking across the edge of the walled city in the third series. The four corners of this world are secure, at least for the time being, and walking alone, perhaps, will not lead anyone outside it.
Kyriakos

These are the balcans of decadence. Try to run to the great church in the second series, or walk the stairs to the parthenon in the first, fall off the windows in the modern industrial set only to find yourself walking across the edge of the walled city in the third series. The four corners of this world are secure, at least for the time being, and walking alone, perhaps, will not lead anyone outside it.
Kyriakos