When Charles I of Spain invited the Knights of St John to take possession of Malta, Birgu was the place they chose to settle, fortifying an area that swelled to become the Three Cities of Cospicua, Senglea and Vittoriosa, renamed in celebration of the Great Siege of 1565. Traces of the Knights are still visible throughout the Three Cities, though less so in Senglea, which received the Coventry makeover that was much in vogue throughout Europe during the early-1940s and entailed entire districts of historic architecture being flattened and replaced wholesale by heaps of rubbish. (In Britain the trend lasted through the 1960s, though an early form of political correctness meant it was known as urban planning rather than aerial bombardment.)
For tourist purposes, the Three Cities turned into the Four Cities in the late-19th century when the British got into the fort building act too, throwing up Fort Rinella to house the state-of-the-art, world's biggest cannon, Armstrong 100-ton gun (it was fired forty times and didn't hit a thing).
Buses from Valletta all stop outside Vittoriosa's Three Gates, a mammoth series of defensive structures which withstood the Great Siege and now, appropriately enough, house the Malta at War Museum (though the steep admission fee proves a deterrent against entry every bit as strong as anything the Knights ever built). It's a short walk downhill from the main gate to the Inquisitor's Palace, home of the Inquisition from 1574 to 1798 and breeding ground for two popes and twenty-two cardinals (experience of enhanced interrogation techniques was evidently as highly prized by the Vatican then as during the later years of the George Bush White House). The area behind here is the Collachio, starter home for the Order before its climb up the island's property ladder. Now a spruced-up warren of ancient streets,these days you're more likely to see t-shirts and ladies' underwear than muskets or swords poking through the upper windows. Almost every corner boasts a plaque from the council expressing its "sincere thanks" to the residents for keeping the area clean, provoking the opposition of dog owners who've allowed their pets to shit everywhere in retaliation.
Behind Victory Square the streets tumble sharply to St Lawrence's Church and the marina, pleasure boats straining gently at their moorings on the crystal-dimpled water. The peninsula ends at St Elmo's Fort, a huge, many-cornered slab of stone taking in Floriana, Valletta and Senglea in one, uninterrupted sweep.