https://www.worldheritagesite.org/
WorldHeritageSite.org is the internet’s largest community of World Heritage Site enthusiasts— yes, such a thing does exist! Established in 1997 by an intrepid Dutch traveller named Els Slots, WorldHeritageSite has over 1,500 members who between them have visited 1,098 of the 1,121 World Heritage Sites. The site has full information for every World Heritage Site, along with “Tentative” World Heritage Sites (which are sites that might get added to the list in future), but the real power of the site is its community.
Members are encouraged to write reviews of their experience when visiting World Heritage Sites, and the result is an incredibly rich collection of insider tips and useful knowledge. This can be contextual background information that isn’t readily apparent from UNESCO’s official documents, general travel tips, hyper-specific detail about the best parking locations, or interesting aspects of the site to look out for.
There’s also a large and active discussion forum where members share their experiences and plans for visiting sites, along with discussing UNESCO’s activities.