TIL in 1956 Paris and Rome signed an agreement to become twin cities of each other exclusively with the statement "Only Paris is worthy of Rome; only Rome is worthy of Paris".

https://en.wikipedia.org/wiki/Paris#International_relations

https://www.reddit.com/r/todayilearned/comments/15munho/til_in_1956_paris_and_rome_signed_an_agreement_to/