Launching on Midsummer's Day with a performance of Tchaikovsky's '1812 Overture' in Guildhall Yard (Jun 21 6pm; free), this four-day event aims to showcase the City while unlocking some of its secrets. Events, many of which are free, include exhibitions, talks, walks, openings of the City's Livery Halls, music in many of its churches and family entertainment at the Cheapside Street Fayre (Cheapside and Poultry, EC2: June 23 10am-5pm; free), as well as events at the Barbican Centre and Museum of London. Family events include 'Open House Junior Festival' (June 23 & 24), a child-friendly architecture festival featuring tours, competitions and other activites. During the Cheapside Street Fayre, St Paul's Cathedral is waiving its admission fee for kids and children will be offered free ice cream and tuk-tuk rides to Leadenhall Market. See the website for updates.