sentences:  The southern gateway into the Bastille became the principal entrance to the castle in 1553, the other three gateways being closed.A bastion, a large earthwork projecting eastwards from the Bastille, was built to provide additional protective fire for the Bastille and the Arsenal; the bastion was reached from the fortress across a stone abutment using a connecting drawbridge that was installed in the Bastille's Comté tower.In 1573 the Porte Saint-Antoine was also altered – the drawbridges were replaced with a fixed bridge, and the medieval gatehouse was replaced with a triumphal arch.