Who is he? A severe master architect who equated ornament with crime. He was also one of the leading lights behind the International Style. Remind me what the International Style was - a multicultural riot of colour? No, quite the reverse. It was a 20th-century design approach marked by its geometric simplicity. Think expanses of glass, flat roofs and an emphasis on the cubic. Decoration was out. What's Loos' story? The son of a stonemason, he was born in 1870 in Brunn, Moravia (now Brno in the Czech Republic). To his mother's horror, he rejected the family business and studied architecture in Dresden before heading to the United States, where he worked as a mason, a floor-layer and a dishwasher. Struck by the efficiency of American architecture, he particularly admired the work of Louis Sullivan, one of the nation's most influential architects. In Loos' biography, author and cultural historian Panayotis Tournikiotis writes: 'Doubtless, Loos felt suffocated in the confined and conservative atmosphere of the Austro-Hungarian Empire, and he thought that in America he would discover realism and freedom, a land where everything was possible.' Even so, Loos wound up back in Europe, opening his practice in Vienna in 1898 and producing his first important work, the Cafe Museum, a year later. He went on to launch the architecture school that spawned writer and architect Richard Neutra. Loos' radical 1908 essay, Ornament and Crime, became an intellectual yardstick for many architects destined to follow in his wake, not least innovative Swiss seer Le Corbusier. Loos became a powerful man, cosy with the likes of Austrian expressionist painter Oskar Kokoschka. His work embodied his belief that 'the building should be dumb outside and only reveal wealth inside'. His sparse exteriors were offset by lavish interiors. What is he best known for? The Villa Muller, built in Prague in 1930. It is equipped with a typically bare exterior. The inside is a mishmash of bright tiles, columns, lemonwood panelling and light. What else did he design that demands attention? The Looshaus (above) on Michaelerplatz in Vienna, which was completed in 1912 and was meant to establish a transition between the imperial palace and a chic street called the Kohlmarkt. There are two other Viennese masterpieces - the Steiner House (1910) and the Rufer House (1922) - and the Khuner Villa, Payerbach, Austria (1930).