 Largely due to immigration from Hungary , Bohemia and Moravia , the Jewish population of Zagreb quickly grew in size : from 1 @,@ 285 members in 1887 to 3 @,@ 237 members in 1900 , and then to 5 @,@ 970 members in 1921 . The synagogue became too small to accommodate the needs of the ever @-@ growing community . In 1921 a renovation was undertaken to increase the number of available seats . A 1931 plan to increase the capacity to <unk> seats was ultimately abandoned . A central heating system was installed in 1933 . 
