In 2009 Spanish architecture firm selgascano opened their new offices in a forest outside of Madrid . They did not erect a structure , but instead inserted their structure — essentially a glass tube — into the forest floor . The north - facing wall of the tube consists of a 2 mm thick curved window . " Working under the trees helps you relax , even in stressful situations , " says Paolo Tringali , an Italian architect at the firm . " The most amazing thing is working eye - level with insects . Living alongside them you adapt to the flow and rhythm of the ever - changing nature . "