Trevi Fountain

According to legend, throwing the appropriate number of coins into the fountain is said to ensure the fulfillment of a wish for the thrower.

An excerpt from the article 18 facts about Trevi Fountain
The tossing of one coin is supposed to ensure a return to Rome, two coins - romance, and three coins - marriage. For the request to be fulfilled, the money should be thrown with the right hand over the left shoulder.