I came across this paper titled "Karst and World Heritage Status" -it may be of general interest. It is dated 2007 with an addendum to report "Karst related" activity at the Jun/Jul 2007 WHC in Christchurch. As well as discussing the criteria appropriate for Karst sites (which often have both Natural and Cultural aspects) the report contains a full list of some 50 WHS which included "Karst" landscape as of 2005

http://carsologica.zrc-sazu.si/downloads/362/hamilton13.pdf

Impressive collection of Karst site and details, even I know that there are many karst sites in WHL, but I never think that place like Luang Prabang, Grand Canyon, Lake Baikal are also considered as karst sites!