German architect, archaeologist and writer. He was one of the leading figures of Berlin’s architectural establishment in the latter half of the 19th century. On completion of his studies in 1852, he was given the prestigious post of Bauleiter at the Neues Museum in Berlin, designed by Friedrich August Stüler. He subsequently became a lecturer and in 1861 a professor of architectural history at the Bauakademie in Berlin. Many of his church buildings used medieval motifs and elements, for example the Christuskirche (1862–8) in Berlin and the Elisabethkirche (1869–72) in Wilhelmshafen. He followed Karl Bötticher in his attempts to merge medieval and classical elements, best illustrated in his design for the Thomaskirche (competition 1862; built 1865–70), Berlin. There, Adler used Gothic structural devices embellished with rich Renaissance detail, a tendency that was also present in many of the entries for the Berlin Cathedral competition (1869). The Thomaskirche became something of a prototype for Protestant churches in Germany. A keen archaeologist, Adler participated in the excavations by Ernst Curtius (1814–96) in Olympia (1875–81). He also designed the Archaeological Museum at Olympia in 1883. After entering the civil service in 1877, he quickly rose to an influential position in the Ministerium für Öffentliche Arbeiten, where he was responsible for church building until his retirement in 1903. He also restored Schleswig Cathedral (1888–94), and the Schlosskirche at Wittenberg in 1892 as a monument to the Reformation. Adler was a member of several national and foreign academic institutes and scholarly societies. He travelled widely in Greece, Palestine and Asia Minor and published numerous articles and books on archaeology and architectural history.
- Die mittelalterlichen Backstein-Bauwerke des preussischen Staates, 2 vols (Berlin, 1859–69)
- Baugeschichtlichen Forschungen in Deutschland, 2 vols (Berlin, 1870–79)
- with E. Curtius: Olympia: Die Ergebnisse, 5 vols (Berlin, 1890–97/R 1966)
- [autobiographical contrib. to] Das geistige Deutschland am Ende des XIX. Jahrhunderts, 1 (Leipzig and Berlin, 1898), p. 8