I have tried to go back to basics on this
a. We started the concept as far back as 2008 (!!
https://www.worldheritagesite.org/forums/index.php?action=vthread&forum=5&topic=5 ) to help us WH Travellers identify WHS which were reasonably "close together" and could therefere potentially "yield" a lot of WHS visits for relatively little travelling..
b. At the time the only tool to help with this which showed WHS was the UNESCO "interactive map" -
http://whc.unesco.org/en/interactive-map/ . It was pretty useless then - and still is!! Zooming is slow and awkward, it doesn't show national boundaries, cities, roads etc, nor individual WHS locations and it has no indication of scale (an early idea was to base hotspots on "radii" from locations on these maps)
c. Since then (2007 WHC) another 242 WHC have been inscribed, many more places/areas have become "Hot spots" and our knowledge of all the WHS and their locations has increased considerably so we understand their locations better -and thus identify more hotspots!.
d. We have introduced our own Mapping - far superior to that of UNESCO, it shows all WH locations and is fully integrated with more detailed maps. We also have preset "country" and also "Hot spot" views to assist with zooming. But it too still has its "weaknesses" - for instance at any particular "zoom" level one cannot easily know the scale.
e. We now have 86 "hotspots" identified and it has actually become a bit hard to know where hotspots are - one has to read all the way through the list to find one (if you know what you are looking for) - and even then do we really know what we are likely to "find" in the "Saxony-Anhalt" hotspot for instance?? If you simply want to know whether there is a hotspot in a particular region then you must "guess" what it might be called! We have also not been entirely consistent in determining and applying "definitions" for hot spots with a tendency to be "creative" in identifying WHS which could be included!
f. One could ask if the Hotspot concept actually adds much now. It doesn't require an Einstein to look at our maps and, reasonably quickly, identify areas with lots of "dots" - on the basis of which we could each do our own individual planning! I think it does but we are still caught between the twin objectives of showing both "geographic proximity" and "travel practicality". My view is that "travel practicality" is too complex a subject to try to cover in a hotspot - both in terms of all the alternative modes available and different "travel styles". (I think of our "joke hotspot" where we showed that Warsaw was achievable in a day return from London!!!) We have reviews for such matters after all.
g. So - I think we should limit definition of Hotspots to "geographic" rather than "travel practicality" rules (whilst still excluding "impossible" transborder or mountain crossings etc!!). I suggest that wee should also address Assif's suggestion for "Cultural hotspots" i.e. all WHs related to Italian, German, French etc "provinces" separately. If we adopt "Geographic proximity as the basis for Hotspots" e.g a strict 200kms radius, Then does it really matter if we duplicate WHS across several adjacent hotspots? If we are going to have tightly defined hotspots however I think we do need a "tool" to identify them and where they are on a bigger map. Also we need to make it easier to see them in relation to each other. A regional Hot spot map could achieve this. It could also be useful if Hotspot maps had a preset (or even "amendable") "Radius circle" on them to show, whatever the zoom, where the 200kms lay? Is this possible?
h. There remains the issue of "Hotspot centres" - if the 200 km rule is to be paramount then the determination and location of the "centre" becomes more important and the area covered is defined by it - but where do we stop - Manchester, Leeds, Bradford, Sheffield and Liverpool each as a separate centre for a Northern England Hotspot?? That would just complicate matters unnecessarily! We need some "rule"/"convention" to avoid excessive duplication and overlaps - possibly along the lines that any "hotspot" needs to have at least 25% (??) of its WHS unique to it?? I don't see that a "centre" actually possessing a WHS is relevant. Also we would need to avoid choosing some tin pot village just because it "conveniently" encompasses an extra WHS within its 200kms radius!!
i. I don't think that the above suggestions would mean a large scale revamp of our existing hotspots - we can take our time to
i. provide the new "Hot spot map" to assist identifying location of hotspots and adjacent ones
ii. Make sure all Hotspots have a centre and a radius on the map if possible?
iii. Review the geographic limits of WHS in each hotspot.
iv Introduce new hotspots where justified