The Megalo Kastro ( = Big Castle) of Chora is one of the three Medieval fortresses preserved on Kalymnos. Its original phase can be dated to the tenth or eleventh century ad, but this remains to be confirmed by a systematic archaeological research. The present form of the castle dates back to the period of the Knights’ Rule (1309-1523) and, although simple, it represents a typical example of the art of fortification before and after the use of gunpowder. The ruins of the Medieval settlement have been preserved inside the castle: ten small Byzantine and Post-Byzantine churches, the frescoes of which have been restored, as well as other significant elements, extremely instructive for the everyday life in the Megalo Kastro Life went on in the settlement, at least, until 1823. In the framework of a project of the Greek Ministry of Culture for the promotion of the Medieval castles of the country, a relevant study has been made for the Megalo Kastro of Kalymnos, and some of its proposals are presented in this article. The necessary works are to be immediately realized, so that the first restored, developed and incorporated in modern life monumental ensemble to be given back to the island.