The Room of Requirement is a room in Hogwarts that only appears when a person is in great need of it. The room then transforms itself into whatever the witch or wizard needs it to be at that moment. It is believed that the room is Unplottable, as it does not appear on the Marauder's Map, nor do its occupants, although this could simply be because James Potter, Remus Lupin, Sirius Black, and Peter Pettigrew never found the room.
It is apparently a more accurate (or at least more accepted) way of predicting the future, similar to an obscure but existing hobby of numerology - the belief that number patterns existing in real life can be calculated to give information regarding the future.
The seventh floor can be quite undetected - though the room of requirement makes it quite debatable. The room of requirement does serve for lusting couples at some points in time - though mischief makers tend to get their hands on it first. Classrooms and offices can be found a way away on this floor, but students still tend to be on the look-out.