The Bermuda Triangle or simply, The Triangle is the curb outside The Apartment. It would be the place where if Ted and Marshall would want to get rid of something they would put it there and by the time they turned around it would be gone.
In Robin 101, Marshall finds his old barrel Mabel from the basement of his apartment building, which he couldn't keep in the apartment because Lily "claimed" that she is allergic to barrel resin. He decided to put it in the triangle to give away but is disappointed when no one takes it. Later, Barney puts a notebook (which was filled with information he got from Ted about Robin to be a better boyfriend to her) on top of Mabel, which disappears in an instant.
Later, in Something Old, when Lily and Marshall are packing for their yearlong move to Rome, with the help of Ted because he's ''packing master", they decide to put the stuff they are not taking to Rome in the triangle. When they talk about what to do with a ten year old beanbag chair, Ted says that they have to take to Rome, much to Marshall and Lily's surprise, as they don't want to do that. They try to convince Ted to leave the chair, but he stays put. Marshall and Lily then send Ted to run an errand, and put the chair in the triangle but Ted realizes that they fooled him and sits on the chair before someone takes it away. When Ted tells the real reason he wants them to take the chair, he asks them to leave him alone to say goodbye to the chair. He then gets up to hail a cab and looks back to see that the chair has disappeared.