The Olympics are huge, expensive multi-sporting events that (in theory) occur every two years (Summer Olym­pics every four years, and Winter Olym­pics every four years between those). They have been controversial because hosting them often requires cities to build costly specialised infrastructure that basically has no use once the games are over. In recent years fewer and fewer cities have even put themselves forward to host the games, and those which have have been less willing to build these kinds of “white elephants”.