King's Cross Station
King's Cross Station is the train station in London, England, which has Platform 9 3/4, the platform the Hogwarts Express departs from once every year on September 1st at 11 AM. It also serves Muggles traveling to and from London. From the King's Cross you can not see platform 9 3/4 as it is a magical platform, and you have to run at the wall, between platform 9 and 10.
In Harry Potter and the Deathly Hallows, when Harry Potter is in Limbo he sees it as King's Cross. This could be taken to symbolize the border between the realm of the living and the realm of the dead.