This page will list all the UNESCO World Heritage Architecture sites with an interactive map. I've been to a few but plan to go to many more over the coming years.
Architectural Digest: 15 UNESCO World Heritage Sites to Add to Your Architecture Bucket List
UNESCO: World Heritage Earthen Architecture Programme (WHEAP)
ArchDaily: 8 Buildings by Frank Lloyd Wright Nominated for UNESCO World Heritage Status
ArchDaily: Rio de Janeiro named the First World Capital of Architecture
arch2o: 10 UNESCO World Heritage Sites by Famous Modernist Architects
Number of Buildings shown: 5
Alphabetical list of included buildings