Platform Nine and Three-Quarters is a magical platform located at the Muggle King's Cross Station in London. It is the departure point for the Hogwarts Express, the train that transports students to and from Hogwarts School of Witchcraft and Wizardry at the beginning and end of each term. To access the platform, a witch or wizard must walk directly through the seemingly solid brick barrier dividing platforms nine and ten. The barrier acts as a magical portal, allowing magical folk to pass through seamlessly while remaining unnoticed by the surrounding Muggles. From the other side, the platform appears much like a standard old-fashioned railway station, featuring a wrought-iron archway overhead bearing the words Platform Nine and Three-Quarters. The platform is typically bustling with students and their families, who are seen with trunks, owl cages, and other magical luggage. The iconic scarlet steam engine of the Hogwarts Express is the central feature, waiting to begin its journey north to Hogsmeade Station. The use of a single, discreet departure point for the Hogwarts Express was established by the Ministry of Magic to provide a secure and orderly method for hundreds of students to travel to Hogwarts without attracting Muggle attention. This method was instituted in the 19th century after various prior methods, such as Portkeys and unregulated travel, proved chaotic and breached the International Statute of Secrecy (Pottermore).
Platform Nine and Three-Quarters serves as a crucial transitional space and a recurring setting for significant moments throughout the series. It is the symbolic gateway between Harry Potter's mundane life with the Dursleys and his true home in the magical world.