This is a bridge in Paris. You hang locks on it with the name of you & your boyfriend/girlfriend/best-friend then throw the key into the river. So even though the friend/relationship may end, you can’t remove the lock. It stays there forever, as relevance
I like tattoos, but I fear regret. Therefore I am a proponent of tattoos that either represent something you will (however complexly) love forever. or something so broad that it's impossible to stop liking (The World). I like this one quite a bit!