Oradea's centre is essentially a museum of late-19th and early-20th-century architecture, with one of the densest concentrations of Art Nouveau buildings anywhere in Eastern Europe. Most of what you want to see is within fifteen minutes' walk of Union Square (Piața Unirii), where the Black Vulture Passage and the Church with the Moon stand within sight of each other. The Roman Catholic complex — the Baroque Palace and the Cathedral Basilica — sits a kilometre north across the Crișul Repede river.