Open House London is an organisation which promotes appreciation of architecture by the general public. It organises tours, lectures, educational projects for children and so on, but it is best known for the Open House Weekend, a two-day event which takes place over one weekend every year in September, throughout the whole of London. It has previously featured five hundred buildings including banks, offices, government buildings, and even private homes. The event attracts tens of thousands of people. It is often possible to turn up and go straight into some establishments, although queues are an hour or two long at the most popular buildings, while in other cases admission is by advance booking of a guided tour only. The Open House event in London is usually held on the third weekend in September. The most recent was held on the weekend of 19 and 20 September 2009.