After the founding of the headquarters on the island of Rhodes, the Knights of St. John began building the castle of St. Peter on the mainland (today Bodrum, Turkey). It was supposed to be another fortress in the Aegean region. Construction began in 1404. The most modern defensive features were implemented. The passages between the gates were full of twists and turns so that potential attackers could not find cover from the archers' fire above. Knights placed hundreds of coats of arms carved in relief over the gates and on the walls. Many of them have survived, incl. coat of arms of the Grand Master Pierre d'Aubusson, coats of arms of commanders, langue and knights.
A langue was an administrative division of the Knights Hospitaller and referred to ethno-linguistic division of the Order's members. At the castle of St. Peter, each langue of the Order constructed their own tower and was responsible for a defense of a specific portion of the fortress. The English, French, German, Spanish and Italian towers are reconstructed.
The heavily fortified fortress could not match the forces of the Turkish Sultan Suleiman the Magnificent, who attacked the knights in 1523. The defeated knights of St. John surrendered and left the Aegean region.
