King's Cross Station

When Ottaline Gambol commandeered a Muggle train to serve as the new mode of transport for Hogwarts students, she also had constructed a small station in the wizarding village of Hogsmeade: a necessary adjunct to the train. The Ministry of Magic felt strongly, however, that to construct an additional wizarding station in the middle of London would stretch even the Muggle's notorious determination not to notice magic when it was exploding in front of their faces.

It was Evangeline Orpington, Minister from 1849-1855, who hit upon the solution of adding a concealed platform at the newly (Muggle) build King's Cross station, which would be accessible only to witches and wizards. On the whole, this has worked very well, although there have been minor problems over the ensuing years, such as witches and wizards who have dropped suitcases full of biting spellbooks or newt spleens all over the polished station floor, or else disappeared through the solid barrier a little too loudly. There are usually a number of plain-clothed Ministry of Magic employees on hand to deal with any inconvenient Muggle memories that may need altering at the start and end of each Hogwarts term.

From Pottermore (www.pottermore.com)