Insider knowledge

Architectural delights ranging from a 1950s bus station to a Georgian horse hospital and from modern houses to the home of William Morris open their doors to the public this weekend as part of this year's London Open House festival (20-21 September).

But it is not just the breadth of building types and styles on show that makes this annual event so special; what is so remarkable about Open House is the willingness of the owners and occupiers of the buildings - more than 500 of them spread from Hillington to Havering - to allow strangers to wander through them. Because most of the properties are private, throwing them open to one and all is a striking example of public spiritedness that is clearly appreciated by the many who come to visit. More than 350,000 architecture-lovers turned up during the two days last autumn.

Adding to the rich mix of buildings that have become regular Open House fixtures, this year sees the arrival of precious new gems such as the stunning neo-classical Victoria House office building in Bloomsbury Square, which is being opened to the public for the first time since it was completed back in the 1930s. With its lavish use of stone, marble and bronze it is both a fascinating essay on early-20th century corporate bravura and a tribute to the refurbishment talents of leading modern architect Will Alsop. Look out for the intriguing meeting room pods suspended in its twin atriums.

Also in the corporate arena, Deutsche Bank's UK headquarters in the City will be welcoming visitors wanting to see the building's contemporary style and its impressive art collection that includes work by Damien Hirst and Anish Kapoor.

For an example of the mundane made magnificent, visit Chiswick Business Park, designed by the Richard Rogers Partnership as an oasis-style workplace for up to 10,000 people and built around a lake with open-air meeting spaces, dramatic landscaping and an arresting collection of sculptures.

In contemporary homes, concrete emerges as a major theme. It makes an appearance used raw and gritty in the chic urban apartments at One Centaur Street in SE1 designed by architects dRMM; it is polished smooth and shiny in an elegant live/work space at 246 Kilburn High Road designed by Denton Corker Marshall, while the team at Azman Owens has built a whole house of the stuff and combined it with glass and timber to make a handsome, award-winning family home in Islington.

Among the historic homes featured is, for the first time, Philip Webb's Red House in Bexleyheath, built for Victorian designer William Morris, which has recently been acquired by the National Trust. From the 18th century is the remarkable Georgian Home House in Portman Square, W1, now a private club. One of the oldest homes on show is the magnificent Tudor mansion Hall Place Bexley, built for a Lord Mayor of London.

Other highlights include the world's oldest film studios at Ealing, now undergoing refurbishment, and the Phoenix Cinema, Barnet, one of the oldest working cinemas in the country.

Following 300 years of limited public access, it is now possible to take a look at the vast complex that is the Royal Arsenal at Woolwich designed by Sir John Vanbrugh with James Wyatt, which is currently being converted into apartments. Alternatively, you could venture to Neasden to visit the wartime bunker used by Churchill. But for the truly esoteric, visit Stockwell Bus Garage to gasp at its innovative 1950s concrete structure.

Alongside these you will find galleries and government buildings, churches and concert halls, hospitals and hotels.