When I first suggested "Linear Sites" I was thinking of Roads, Railways and Canals where just the "narrow" (and man made) item itself was inscribed. "Rivers" as natural rather than man made features only came in as a second thought - but some sites certainly follow them in a "line" in the form of cultural/man made structures/landscape much the same as a canal so, it seemed, they fitted the idea. On any of them some allowance obviously has to be made for buildings, towpaths, stations etc running alongside the basic "line" - but that then raises the issue as to how far beyond the "line" we go and still have what is basically a "line"?
In some of its evaluations UNESCO also actually referred to the concept of a "Linear Landscape" - which would seem to suggest that this aspect of a site has some wider validity but unfortunately it does not appear to have been universally used so we can't rely on its use as the prime determinant of this connection
It is a judgement call - The Middle Rhine Valley certainly "follows" the Rhine Valley in general but also includes a lot of areas some distance away from the river. The Map in the Nomination file is rather awkward to follow but shows that the boundary frequently "wanders" away from the Rhine banks themselves up other valleys and even over hills. This map shows it on a single page http://en.wikipedia.org/wiki/File:Karte_Mittelrhein.png
At almost no point does the site solely follow the banks of the Rhine
On the other hand the "Banks of the Seine" very much emphasises the banks with their man-made features and, although it does depart from the streets and buildings immediately fronting the Seine (eg for the Eiffel Tower), the vast majority of the site directly faces the Seine.
What about Lavaux - which follows the north shore of Lac Leman? (But not really a "central" line?)
What about Quebrada de Humahuaca which follows a wide mountain valley
This is all a "game" of course but in so far as it has a purpose it is to highlight something worth knowing and possibly unusual about a site and other sites sharing that attribute. I certainly "learned" something when I looked at the map of the Incense Route and Desert Cities of the Negev (suggested by yourself Assif?) and discovered just how "linear" it was!
I personally don't feel that the Middle Rhine inscription really "connects" with the others in terms of its "linearity".
BUT of course we could
a. Extend the, admittedly arbitary, "5kms" rule.
b. Grind even smaller by introducing other rules about percentages of length being linear or within sight of a "central" line etc etc.
c. Introduce a new connection for "River Valleys" and limit the "linear" connection to man made objects
d. Allow linear to mean roughly longer than narrower
e. etc etcINDIGENOUS POPULATIONS IN NATURAL SITES
This Web site contains data sheets on all (??) Natural WHS - each Data Sheet includes a statement on whether there is a permanent human habitation and, if so, by what sort of people. http://www.unep-wcmc.org/sites/wh/index.html
Sometimes it isn't absolutely clear whether an identified population actually lives inside or at the edge of a site - e.g for Nahanni it states "Some 100 Nahanni Denes follow a traditional way of life at Nahanni Butte at the junction of the South Nahanni and Liard rivers at the southern end of the Park"
. You need to go to Parcs Canada to discover that Nahanni Butte is indeed at the southern end of the park, but it is also just outside!!
The Rocky Mountain Parks data sheet makes no mention of any indigenous groups living inside those parks.
The Wood Buffalo sheet states "The local Cree and Chipewyan tribes are now organised into the Mikasew-Cree First Nation and exercise fishing, hunting and trapping rights in the Park." - but we already have another connection for traditional Hunting. It then states "some trapping permit holders live in the Park during the winter" . Over to you on that one Els - does "living in the park during the winter" constitute habitation as per the Connection??
I am sure a trawl through these Data Sheets would identify other sites for this Connection - Dja for instance.