Imagined by New York-based Holl as a "vessel within a vessel within a vessel", the luminous Maggie's Barts features a concrete frame, a layer of bamboo wood and a skin of matt glass.
It is located at St Bartholomew's Hospital to the northwest of the City of London – a facility that was founded in the 12th century, making it the oldest hospital in Britain.
Maggie's Centres offer free practical, social and emotional help to anyone effected by cancer. There are already a number of these centres around the UK, by architects including Rogers Stirk Harbour + Partners, OMA and Snøhetta.
Holl's design pays tribute to the building's medieval heritage. The geometric facade is modelled on the medieval method of writing down music, called "neume notation". It features lines at 90-centimetre vertical intervals, interspersed with the colourful glass panels.
"The word neume originates from the Greek pnevma, which means 'vital force'," said Holl in a statement.
"It suggests a 'breath of life' that fills oneself with inspiration like a stream of air, the blowing of the wind. The outer glass layer is organised in horizontal bands like a musical staff while the concrete structure branches like the hand."
The glass envelope washes the interior with colour during daylight hours. Lit up at night, it glows from within.