i think the Ingress Portal criteria is a good starting point:
A LOCATION WITH A COOL STORY, A PLACE IN HISTORY OR EDUCATIONAL VALUE
A COOL PIECE OF ART OR UNIQUE ARCHITECTURE
A HIDDEN GEM OR HYPER-LOCAL SPOT
PUBLIC LIBRARIES
PUBLIC PLACES OF WORSHIP
Avoid:
Candidates in locations with NO SAFE PEDESTRIAN ACCESS.
Candidates of PEOPLE, BODY PARTS, LIVE ANIMALS, etc.; please, just don’t.
Candidates that are NATURAL FEATURES (Includes pictures of landscapes as well as submissions where the subject is a lake, river, stream, mountain, volcano, waterfall, etc.; does not include man-made points of interest - plaques, signs, etc. - near natural features).
Candidates that are NOT PERMANENT, including SEASONAL DISPLAYS that are only put up during certain times of the year.
Candidates on PRIVATE RESIDENTIAL PROPERTY (including farms)
Candidates that may interfere with the operations of FIRE STATIONS, POLICE STATIONS AND HOSPITALS
Candidates on the grounds of PRIMARY/SECONDARY SCHOOLS
https://support.ingress.com/hc/en-us/articles/207343987-Candidate-Portal-criteria