Roman Catholics on Sunday gathered in the Cathedral of the Immaculate Conception in Portland to celebrate its 150th anniversary. Still Portland’s tallest building, the cathedral in the East End was completed after the Great Fire of 1866, which had destroyed its nearly completed walls. The cathedral was dedicated on Sept. 8, 1869. Bishop Robert P. Deeley celebrated a special Mass on Sunday in commemoration of the anniversary. The event fell on Feast of the Nativity of the Blessed Virgin Mary, who is prominently featured on the cathedral’s stained-glass windows. Tours of the historic structure take place on Sunday mornings after Mass. Anyone seeking information about the structure or to schedule a special tour may call the parish office at 773-7746.