Found outside Chiesa dei Santi Vincenzo e Anastasio, near the Trevi Fountain. Love struck couples write their names on the locks, attack them onto the gate and chuck the key away, presumably into the fountain. Last I heard, church authorities were not amused and were actively trying to initiate a lock-down (ahem) on this practice, which presumably costs them a minor fortune in removal fees. I’m not sure if they have thrown their hands up in the air yet, or if the love-struck couples have found a different place on which to latch their tokens of affection.
If it were me, I’d want my significant other to trawl the nearby fountain for money, as a sign of her affection. Heh.