And Jon Naar, author of "Design for A Livable Planet, " suggests that 15 to 20 plants are enough to clean the air in a 1, 500 square foot office area (139 square meters).

CNN: Office foliage for feel good factor

The article 'Mini guide to design in Helsinki' was published in partnership with Lonely Planet Traveller.

BBC: Mini guide to design in Helsinki

It is not easy to find critics of the new design - most guides seem to agree with London's Lonely Planet Guide that it has undergone "a remarkable transformation", making it easier to appreciate the buildings flanking it.

BBC: Successful London Olympic bid celebrations