Tower and Gate of St. Paul (Post of France), Fortress of Rhodes.

The construction of the complex of fortifications near the Grand Master's Palace was begun under Jean de Lastic (1437 - 1454), who also built the Cannon and St. Anthony Gates, as well as the Battery of the Olives.  Pierre d' Aubusson (1476 - 1503) had it strengthened with a thick earthen outwork, which was cut through with a gate (d'Amboise Gate) under Emery d'Amboise 1n 1512.  In 1514 Grand MasterFabrizo del Carretto had a caponier built in the ditch on the extreme north-west cornerof the fortress, beyond d'Amboise Gate.  The Gate of St. Paul as protected from the outside with a polygonal barbican.  Although the walls of the barbican were adjusted to accomodate artillery, they were fairly thin and crowned with a merloned parapet.

outwork -- Any defensive structure in front of the main enciente;

caponier -- A covered defensive passagemade in a dry ditch projecting away from the main enciente in the direction of te enemy.  It is sometimes connected to the main enciente with outworks.  It was chiefly designed for laying flanking fire along the ditch;

barbican --An outwork designed for the defence of agate or a bridge leading to a gate;

merlon --The upstanding sections of a parapet between embrasures, behind which defenders can shelter;

parapet -- A bank, of earth, or a wall over which a soldier may fire; also known as a breastwork;

enciente -- Th outline of the main line of defences, excluding minor outworks;

embrasures -- An opening in a parapet allowing artillery to fire through.

References:--

-Konstantin Nossov, "The Fortress of Rhodes 1309-1522," (Osprey, 2010);
-Ian Hogg, "The History of Fortification," (St. Martin's Press, 1981).