With the Olympics fast approaching, thousands of visitors are getting ready to descend on London. If you’re one of them, you should know that the British capital is a big place, and there’s no grid system, meaning you really need some inside gen ahead of time if you want to make the most of your trip.London cab drivers study something called ‘The Knowledge,’ which enables the best of them to find any street in the city–but it’s a rare ability, and let’s be honest, you just don’t have the time before the Olympics starts. Instead, you could invest in the Rough Guide to London … and if you don’t fancy lugging the book in your carry-on, a new app might be just your cup of tea. Featuring GPS mapping for the city center, and geo-coding on the maps, getting lost is harder than ever. Pre-trip the app enables you to bookmark an itinerary; and if you can’t decide what to do, there’s a “lucky dip” feature that conjures up suggestions of fun places to visit.