As part of Open House London 2012, the grade I-listed Royal College of Physicians (RCP) will be open to the public on Saturday 22 September 2012 between 11am and 4pm.

The RCP isn’t the only modernist masterpiece taking part in Open House; this year the event includes more post-war architecture than ever before. To help you navigate the plethora of brutal buildings, we asked architectural expert Barnabas Calder to select his top five:

1. Royal College of Physicians
11 St Andrews Place, NW1 4LE

The grade I-listed masterpiece of Sir Denys Lasdun, architect of the National Theatre, is at the extremely elegant end of modernist architecture. It shows the architect’s respect for the RCP’s fine collection of art and artefacts, with exceptionally opulent finishes of marble, porcelain, and specially-made dark brick. Its internal spaces are generous and airy – don’t miss the sensational staircase hall – and frame beautiful views across to John Nash terraces beyond in Regent’s Park.

2. Alexandra Road/Stoneleigh Terrace
Alexandra Road, NW8 0SF / Stoneleigh Terrace, N19 5TY

During the 1960s architects increasingly avoided tower block housing in favour of densely-packed low-rise. Two of the pioneering estates in Camden are open this year. Alexandra Road is the best-known, whilst the less famous Stoneleigh Terrace has a more private, secluded feel.

3. Balfron Tower/Trellick Tower
St Leonard's Road E14 0QT / Golborne Road, W10 5UT

Take your pick this year between Ernö Goldfinger’s wonderful towerblocks, each recognisable from dozens of films and music videos. Trellick, in Westbourne Park, is later, taller, sleeker in profile, and better-known. Balfron is in Poplar, and whilst the main tower is less glamorous than Trellick, it has more smaller blocks around it which makes for a more impressive setting.  Balfron is in Poplar, so don’t miss saying goodbye to Alison and Peter Smithson’s threatened Robin Hood Gardens estate when you’re there.

4. The Barbican/Golden Lane
Golden Lane Estate, EC1Y 0RN / Lambert Jones Mews, EC2Y 8DP

There are flats open in the Golden Lane and Barbican estates, and the Barbican has two different tours; an architect’s studio, and the Guildhall School. The magnificent solidity and roughness of its concrete and the palatial grandeur of its scale and unity are always enjoyable. Best of all, the behind-the-scenes access during London Open House lets you see some of the bits you’d normally miss.

5. Langham House Close
Langham House Close, TW10 7JE

James Stirling and James Gowan were at the heart of Brutalism in the late 1950s, when they designed this small estate of flats. With lots of chunky timber and tough brick and concrete, the flats nevertheless have a thoroughly human domesticity, highlighted by pleasingly conspicuous fireplaces and nicely-shaped rooms.