If you follow the Tucson Murals Project blog, you probably saw yesterday's entry Mural-rich street in Guanajuato, México. That door shown above is near the uphill end of this tiny street (not big enough to be a calle, it's a callejon). Instead of a box or a slot that drops letters to a drier spot inside, there's just a bright polished metal correos (mail) slot that drops letters down to street level. (Maybe the letter carrier has some plastic grocery bags handy for rainy days?)
I wandered by on March 11, 2017.