The Missing Post Office [Wikipedia via Atlas Obscura] is a heartwarming art exhibit in Miyoto, Japan. Originally meant to be a temporary art exhibit, the Missing Post Office was created in 2013 by Saya Kubota for the Setouchi Triennale art festival. The exhibit is on the island of Awashima in Kagawa Prefecture and operates out of a 50-year-old former post office.
At the Post Office, people can send letters to people who can't receive them; maybe an ex lover, or a loved one who has passed away. Visitors can leave a letter at the exhibit, or take one home if they feel it's meant for them. I imagine this must be a cathartic experience to participate in, and I hope to be able to visit here someday.
The Missing Post Office receives mail from all over the world. Addressees include deceased individuals, future descendants, first loves to whom the writers were never able to express their feelings, themselves, and long-time favorite items. Letters to the deceased are especially common. The sender's name does not need to be written, and the item is sent as "Missing Post Office general delivery". The Missing Post Office prefers postcards to sealed letters. "Posting sets" with the Post Office's address are sold there, and some visitors write messages on the spot.
As of November 2022, the Missing Post Office is open from 13:00 to 16:00 on the second and fourth Saturdays of the month. Only postmaster Nakata is usually present. Received pieces of mail are displayed as works of art and can be read by anyone, but staff do not know what message is in which Post Office Box, and after being read, there is no guarantee they will return to the original Post Office Box and will instead continue to "drift". A visitor who believes a message is addressed to them is permitted to retain it.
See Also: The informal post office in the middle of the ocean