VIENNA - In the tour books and saccharine-sweet postcards at souvenir shops, the skyline of many historic city centers declared World Heritage Sites by UNESCO looks like it is still dominated by the turrets of the local castle, palace or cathedral. But that is a mistaken impression that was deliberately created to prevent any damage to tourism. The reality is completely different, as alert tourists will discover upon visiting those sites, and as was made clear at the emergency conference of UNESCO (the United Nations' Organization for Education, Science and Culture), which took place in Vienna last week under the slogan "World Heritage and Contemporary Architecture."

The conference dealt with the mutual relations between conservation and development at heritage sites, and the sharp clash between two contradictory forces: the desire to preserve an existing historic and architectural heritage versus the need for renewal and the fear, which is frequently realized, that heritage sites will be Disney-fied and turned into toy cities for tourists and the rich. As was widely reported by the European media, the conference drew a record number of 600 participants, architects, urban planners and decision-makers, which attests to the central place this topic occupies in the public arena.

The immediate catalyst for the conference was a series of high-rise construction projects being promoted across from the Cologne Cathedral, which was declared a World Heritage Site in 1996. But in view of the construction boom, UNESCO last year placed the cathedral on the World Heritage in Danger List - to Cologne's shame. That is one step before removal from the heritage list, a move considered a doomsday weapon - a real badge of infamy.

Other European heritage sites are at the center of similar dilemmas in London, Vienna and also in Prague, where a number of skyscrapers are going up in contradiction to UNESCO principles, thus jeopardizing the city's heritage status.

UNESCO has so far issued fairly clear guidelines concerning the conservation of historic monuments and of the "buffer zones" between them and other areas of a city, which are also under certain restrictions. Those are no longer sufficient, UNESCO found, so an amended policy was formulated ahead of the conference. Its main thrust: recommendations to apply strict regulations to broader areas that have been designated a "historic urban landscape," and to give the conservation guidelines legislative power.

"There must be a limit to designing whatever you want when you are in a city with a long history," the director of UNESCO's World Heritage Center, Francesco Bandarin, told the press after the conference. "We look at what's happening at the 200 heritage sites around the world and we're very worried," he added.

The recommendations will be submitted in July for the approval of UNESCO's World Heritage Committee, and member countries will be asked to sign the memo, the draft for which has already elicited quite a lot of resistance and criticism. From the mayor of London, for instance, whose high-rise construction policy clashes with the UN body's recommendations. According to British architect Piers Gough: "UNESCO is trying to rewrite history." He added, somewhat justifiably, that there is something awe-inspiring in the relationship between existing and contemporary structures, and "over-regulation might reduce cities to a level at which they will merely arouse a soporific pleasantness."

Tel Aviv's White City, which was admitted two years ago to the prestigious World Heritage club, never came up during the discussions in Vienna, despite the presence of senior officials from the Tel Aviv-Jaffa Municipality - city engineer Danny Kaiser and deputy mayor Doron Sapir - and despite the fact that it is in no less danger than the center of Cologne. In Cologne at least they don't dare touch the cathedral itself. Tel Aviv's "cathedral" - the Mann Auditorium - is wantonly being abandoned to far-reaching alterations. UNESCO needs to be informed of what's going on here; the Mann Auditorium is just one example. Perhaps the threat of being kicked out of the heritage club will do the trick.