the colosseum went through big changes of use during the medieval period. at the end of the 500's, a small church had been built into a part of the building. the arena was used as a cemetery. the areas under the seating was used for houses and workshops. there are records of the space being rented as late as the 1100s. about 1200, the frangipani family took over the colosseum and made it into a castle.