In front of the main auditorium of my city they have installed a giant Periodic Table of Elements made of concrete cubes, with each symbol and number engraved in them, and colourful plaques in which there are explained each element in several languages. There you can find plenty of letters and numbers and walk thru them looking for some particular one.
I stopped to take a pic of the calcium, maybe because I need it so much for my bones.
And finally, some different letters, the ones for the blind. This is a touristic guide at the door of an ancient historic building near my home in braille. It explains that it’s a civil gothic construction from the XIV century that has been always in use as the accounts tribunal for the kingdom of Navarre.