“Work on historic buildings is much more difficult than designing new ones,” says Christina Seilern, founder of London-based Studio Seilern Architects. “Everything you do is scrutinized in minute detail, and there’s always the fear of getting it wrong.” As she recounts the 13-year project to create 143,000 square feet of apartments, offices, and leisure facilities from an 18th-century hospital in Vilnius, the capital of Lithuania, one can see what she means. The architects’ bold approach to a sensitive setting required confidence and strong powers of persuasion, but the harmonious accord between restored structures and imaginative additions should put any doubts to bed.