Complex sentence: Pope Gregory XVI (1831--1846) established the Museo Profano Lateranense (or Museo Gregoriano Profano) in 1844 which was made up of statues, bas-relief sculptures and mosaics of the Roman era.
Split into simpler sentences: Pope Gregory XVI (1831--1846) established the Museo Profano Lateranense (or Museo Gregoriano Profano) in 1844. Its collections initially consisted of statues, bas-relief sculptures and mosaics of the Roman era.