The emperor also had a passion for gladiatorial combat, which he took so far as to take to the arena himself, dressed as a gladiator. The Romans found Commodus' naked gladiatorial combats to be scandalous and disgraceful. It was rumoured that he was actually the son, not of Marcus, but of a gladiator whom his mother Faustina had taken as a lover at the coastal resort of Caieta. In the arena, Commodus always won since his opponents always submitted to the emperor. Thus, these public fights would not end in a death. Privately, it was his custom to slay his practice opponents. For each appearance in the arena, he charged the city of Rome a million sesterces, straining the Roman economy.