At the beginning of the 20th century, Riga became the economic and cultural centre of the Baltics. Most of the architects working there were trained at the Riga Polytechnic Institute (RPI), where the School of Architecture was opened in 1869. The architecture of Riga also significantly influenced the development of architecture in the wider area. A number of Jewish architects made notable contributions. Mikhail Eisenstein, Paul Mandelstamm and Jacques Rosenbaum stand out among them. Eisenstein studied in St. Petersburg, but Mandelstamm and Rosenbaum were graduates of RPI. Apartment houses built by Eisenstein at Alberta Street in Riga are well known. The facades of all these structures are reminiscent of magnificent decorations, which literally arise from the lush richness of a variety of unusual ornaments. Mandelstamm was a unique personality in the history of Riga architecture. His creative heritage includes excellent works of three different stylistic periods – Eclecticism, Art Nouveau and Modern Movement. The commercial and residential building at Elizabetes iela 51 (1928) in Riga is a remarkable monument of early Modern Movement. Mandelstam was one of the pioneers of this style. Rosenbaum was one of the most famous Estonian architects in the first third of the 20th century. Some of the buildings created by him are masterpieces that can be seen from afar while at the same time blending harmoniously into the urban environment. The architect also worked outside of Tallinn, where his most famous work was the Laupa Manor Mansion (1910–1913).