The pock-marked facade of the structure in its current state is a result of the removal of iron clamps which were originally used to hold the blocks of travertine together. In the post-Roman period these clamps were more valuable when melted down as raw materials than they were holding these blocks in place. Approximately 300 tonnes of metal, it has been estimated, was used in the construction of the Colosseum.
Notes
Unlike most of the major monuments in Rome including in this database the facing of the Colosseum consists almost entirely of travertine, not marble.
