The International Criminal Police Organization is an organization facilitating international police cooperation. It was established as the International Criminal Police Commission in 1923 and adopted its telegraphic address as its name in 1956.
From the outside of the I.C.P.O. headquarters it can be seen a large building complex with international flags flying outside of it (seemingly like the UN General Assembly). Within the inside of the I.C.P.O. headquarters there is a discussion room, containing rows of seats and tables where different representatives from each country will sit at. The representatives sit facing a giant theatre screen that can be used to display live broadcasts from other people (L once used to the screen to broadcast to the representatives).
INTERPOL is alerted when criminals around the world start dying of heart attacks. Fearing the worst, they call for assistance from L, the world's greatest detective. Watari informs them that L has already been investigating the case at hand and agrees to cooperate in order to track down the vigilante known only as "Kira."