Bernini made magisterial use of the shallow transept available to him. He presented the composition as a theatre facing out into the presbyterium. Bernini also extended the fabric of the chapel upward and outward, as can be seen on the left exterior wall of the church. The altar is surmounted by a bowed propylaeum with two pairs of Corinthian columns in black and white breccia, supporting an ornate pediment with the central section recessed, which frames the famous sculpture. The altar frontal is a relief of the Last Supper in gilt bronze.