What's behind the doors?

New on the list of architectural delights open to the public this weekend will be the Real Tennis Court at Middlesex University in Hendon.

With solid and translucent walls, heated floors and a roof that has been specially designed to let in shadow-free daylight, it's a classic illustration of the architectural theory that form follows function.

From hard hitting balls to perfect peace. This is the transition to the Southgate and District Reform Synagogue.

This serene and contemplative space was originally a Seventies gymnasium that was transformed into a refreshingly simple, modern and spiritual prayer hall with a raked wall, curved ceiling and tear-drop apertures.

Another architectural jewel is Grovelands House which is set in eight acres of private parkland in Southgate. Built in the classical style by the famous architect John Nash in 1797, it is dominated by giant Ionic columns and is now home to the Principal Theatre Company and a private psychiatric hospital, which for a time was home to Chilean dictator Augusto Pinochet.

To experience what life was like in the 17th century, you can visit the oldest surviving home in Hendon, better known as the Church Farm House Museum in GreyHound Hill.

At the University of London observatory, you can gaze at the stars through a 24-inch telescope, and study one of the early examples of a reinforced concrete structure.

East Finchley boasts of two 1930's architectural delights. The London Underground Station with its curved glazed staircases and the Art Deco wall reliefs in the Phoenix Cinema, which introduces viewers to a stylishly rich and decorative period in design.

There are two notable halls in Barnet. The town hall with its lively brick and stone free style facade, and the Tudor Hall.

Through the centuries, churches have given architects the opportunity to devote themselves to the glory of God. The Hampstead Garden Suburb Free Church is Grade One listed with a low concrete dome and a distinctive Tuscan interior.

St Jude on the Hill is Sir Edwin Lutyen's finest church and displays an eclectic mix of styles. St Mary's Church is a 13th century Gothic masterpiece with a delightful interior and built by Fred Rowntree in 1913. The Friends Meeting House is a delightful chapel modelled on the 1688 Meeting House at Jordans in Buckinghamshire.

Finally, the Hampstead Garden Suburb Artisans' Quarter Walk is a guided walk through an artisans' quarter, laid-out terraces and picturesque vernacular cottages. These form part of an aesthetically satisfactory 20th century garden suburb.

Admission is free to all buildings. For information telephone 09001 600 061. Calls charged at 60p per minute.

Places to visit:

The buildings and walks in Barnet that will be open to the public during the London Open House Weekend are: Church Farmhouse Museum, Greyhound Hill, Hendon: Saturday 10am to 1pm or 2pm to 5.30pm and Sun 2pm to 5.30pm; East Finchley London Underground Station, High Road, East Finchley: Sunday 1pm to 5pm. Pre-book only on 020 7267 7644. Friends Meeting House, North Square, Hampstead Garden Suburb: Sunday 2pm to 5pm; Phoenix Cinema, 52 High Road, East Finchley: Sunday 10am to 5pm; Real Tennis Court, Middlesex University, Hendon: Sunday 10am to 5pm, Southgate and District Reform Synagogue, 120 Oakleigh Road North Sun: 1pm to 5pm, Grovelands House, The Bourne, Southgate: Sun 11am & 12pm. Pre-book on 020 8882 8191, Town Hall, The Burroughs, Hendon: Sat/Sun 10am to 1pm, Tudor Hall, Barnet College, Wood Street: Sat 10am to 1pm, University of London Observatory, 553 Watford Way, Mill Hill Park, Mill Hill: Sat/Sun 1pm to 5pm; Hampstead Garden Suburb Free Church, Central Square, Garden Suburb: Sun 1pm to 5pm; St Jude on the Hill, Central Square, Hampstead Garden Suburb: Sunday 1pm to 5pm; St Mary's Church, Church End, Hendon: Sat/Sun 10am to 5pm; Hampstead Garden Suburb Artisans Quarter Walk, Garden Suburb Gallery, Hampstead Way: Sun 1pm & 2pm.