But Helsinki has a lyrical cast that speaks of fin de siecle optimism, defined by the radical architecture sweeping Europe circa 1900: Art Nouveau. However whimsical it looks to us now, Art Nouveau — or Jugendstil (German for “youth style”) — was revolutionary, Modernism’s first stirrings 20 years before the Bauhaus emerged in Germany. Art Nouveau was born in Brussels in the early 1890s, and quickly came to define large parts of cities like Barcelona and Paris. But Helsinki, with 600 Jugendstil buildings, is an overlooked wonderland that unspools like a series of stage sets. His design, in the National Romantic style — a rough-granite version of Art Nouveau — took its inspiration from Finland’s medieval churches.