The Knights of St. John were warrior monks who defended pilgrims to the Holy Land, their order founded in Jerusalem during the Crusades. Expelled from successive bases - Jerusalem, Cyprus, Rhodes - they received Malta from Charles V in 1530 and transformed it into their final fortress. The Great Siege of 1565 saw 40,000 Ottoman troops attempt to dislodge 6,000 defenders; the Knights' survival made them legends and made building Valletta inevitable.

The city the Knights built reflected their character - austere externally, magnificent internally, the limestone facades hiding palaces whose interiors dripped with gold. The Order's eight langues (national divisions) competed in building the grandest auberges (national headquarters), the architecture expressing rivalries that the Order's structure required. The Knights ruled Malta until Napoleon expelled them in 1798; the buildings they left behind define what Valletta is.

St. John's Co-Cathedral is the Knights' supreme monument, the church that holds two Caravaggio paintings and floors made of 400 marble tombstones commemorating Knights who died in the Order's service. The exterior is plain limestone, deliberately humble; the interior explodes in Baroque excess, every surface gilded or painted or carved. The contrast between outside and inside was intentional, the Knights' austerity in public hiding magnificence in private.

The Caravaggio paintings - The Beheading of John the Baptist and St. Jerome Writing - are Malta's greatest treasures, the works that brought the troubled genius to the island where he painted in exchange for being made a Knight. Caravaggio's time in Malta ended badly, as most things in his life did; the paintings remain, their darkness and intensity matched by the church's overwhelming decoration.

Valletta's fortifications were the most advanced of their age, the bastions and ditches and curtain walls designed to withstand the artillery that the 1565 siege had proven deadly. The walls rise 60 meters from the harbors below, their zigzag patterns creating killing zones where attackers would be exposed to fire from multiple directions. The fortifications were never tested - no enemy attempted what the Ottomans had failed.

The fortifications now provide the walks and views that visitors treasure. The Upper Barrakka Gardens on the bastions overlook the Grand Harbour, the noon cannon that fires daily continuing a tradition that once signaled time to ships. The walls that were built to exclude now frame the views that include; the military engineering that defined Valletta has become its scenic infrastructure.

The Grand Harbour is what made Valletta possible, the deep natural port that could shelter entire fleets and that maritime powers needed to control Mediterranean trade. The Knights chose this site because the harbour could be defended; the city they built made defending it possible. The Three Cities across the harbour - Vittoriosa, Senglea, Cospicua - predated Valletta and held the Knights' first fortifications.

The harbour remains active, cruise ships now docking where galleys once moored, the container traffic that feeds Malta's economy mixing with yacht marinas. The view from Valletta across the water to the Three Cities encompasses the geography that determined Malta's history - the harbours that everyone wanted, the fortifications that the Knights built to keep them.

Valletta was Europe's first planned city, the grid that the Knights imposed replacing the organic growth that medieval cities displayed. The main street - Republic Street - runs the peninsula's spine, the side streets descending in straight lines to the harbours on either side. The planning was military, the grid allowing defenders to move quickly and to fire down streets at attackers; the effect is civic, the order creating legibility that tourists appreciate.

The streets hold the life that planning cannot create - the cafes that spill onto pavements, the shops that cater to residents as well as visitors, the churches whose masses continue traditions older than the city itself. Valletta is small enough that every street becomes familiar after days, the repetition building knowledge that longer visits reward.