 Due to the then stringent fire-safety requirements, the extension has a framework of steel and reinforced concrete, with reinforced concrete stairs, an iron construction supporting the large glazed roof and metal windows.After graduating at the Polytechnical Institute, Usko Nyström (no relation) had continued his studies at the École des Beaux-Arts in Paris in 1890-91; on returning to Finland he initially designed (from 1895 to 1908 in the partnership Usko Nyström-Petrelius-Penttilä) neo-Renaissance architecture - in particular gaining from the growth area of building speculation in middle-class apartment buildings in Helsinki - whilst also developing a more Jugendstil style inspired by National Romanticism, and politically by the pro-independence Fennoman movement.Usko Nyström's chief work, the Grand Hôtel Cascade, Imatra (1903) (nowadays called Imatran Valtionhotelli), is a key Jugendstil style building; the "wilderness hotel", built next to the impressive Imatra Rapids (the biggest in Finland), was intended mostly for wealthy tourists from the Russian Imperial capital of Saint Petersburg, while its architectural style was inspired by Finnish National Romanticism, whilst taking its inspiration partly from the medieval and neo-Renaissance French châteaux Usko Nyström had seen during his time in France.