In J.K. Rowling’s Harry Potter series, the Hogwarts Express departs from Platform 9¾ at London’s King’s Cross station.
The hidden platform is introduced in Harry Potter and the Philosopher’s Stone. Harry reaches it with help from the Weasley family, who show him how to pass through the barrier between platforms 9 and 10. The train then carries students to Hogsmeade station near Hogwarts.
Platform 9¾ is a fictional magical location, but Rowling chose King’s Cross because she associated it with journeys to Scotland and had used the station while travelling. The platform number creates a memorable visual joke: it lies between the ordinary platforms numbered 9 and 10.
King’s Cross station later installed a real Platform 9¾ sign and luggage trolley for visitors. That attraction is a tourist feature, while the magical platform in the novels is reached through enchantment rather than by an ordinary railway route.