Subject
- Rock Formations26
- Citadels25
- Abbeys24
- Health Care24
- Events23
- Arches22
- Health Care Facilities22
- Hospitals22
- Canal Construction21
- Doors21
- Railway lines21
- Religion21
- Strasbourg Cathedral21
- Fountains20
- Gun Emplacements20
- Saint Catherine's Monastery (Sinai)20
- Arms and Armaments19
- Exhibitions19
- Philadelphia Centennial Exposition, 187619
- Artillery18