Few port calls begin right in the middle of a capital. This one does. The ship slowly makes its way up the Thames estuary, passes the glass towers of Canary Wharf, then comes to a stop mid-river, facing the twin domes of the Old Royal Naval College. Tenders take over and drop you at a floating pontoon, a few metres from one of the most famous baroque ensembles in England. London is all around, but Greenwich keeps its own pace: that of a sailors' town that became the keeper of the world's time.

The Cutty Sark, a First Salute to the Past

A stone's throw from the landing, a black hull trimmed with gilding dominates the square. The Cutty Sark, launched in 1869, was among the fastest merchant sailing ships of its day. It brought back tea from China, then wool from Australia, at a time when a ship's speed made its owners' fortune. Carefully restored after the 2007 fire, it now rests in a glass cradle: you walk beneath its copper-sheathed keel, an astonishing experience that gives a sense of these greyhounds of the sea.

Wren's Domes and the Painted Hall

Just behind open the courtyards of the Old Royal Naval College, designed by Christopher Wren, the architect of St Paul's Cathedral. The former hospital for seamen houses the Painted Hall, a ceremonial room whose painted ceiling took James Thornhill nineteen years to complete. It was here that Admiral Nelson's body lay in state after Trafalgar. You enter speaking softly; you leave with a crick in your neck.

From the Maritime Museum to the Meridian

Continuing toward the park, the National Maritime Museum unfolds several centuries of naval adventure, from navigation instruments to great voyages of exploration. Admission is free, as at most major British museums. Next door, the Queen's House preserves its famous spiral staircase nicknamed the "Tulip Stairs." Then comes the climb, gentle but real, across the lawns of Greenwich Park to the Royal Observatory. The Prime Meridian runs through its courtyard: a brass line set in the ground separates the Eastern and Western Hemispheres, and everyone has fun placing one foot on each side of the planet. From the terrace, the view takes in the bend of the Thames, the skyscrapers of the City and the white dome of the O2.

The Market and the Village Streets

Back down in the centre, the town returns to its village face: Georgian lanes, bookshops, pubs weathered by time. Beneath the glass roof of Greenwich Market, artisans, antique dealers and street-food counters share about a hundred stalls. It's the perfect place to eat without straying from the river, between a slice of pie and a cone of churros.

Venturing into Central London

If time allows, the capital is within easy reach. Two simple options are open to passengers:

• the DLR, an automated light rail, links Cutty Sark station to the City in about twenty minutes;
• river buses leave Greenwich Pier for Tower Bridge and Westminster, with the Thames as your avenue.

Tower of London, Westminster Abbey, Changing of the Guard: everything becomes accessible, provided you keep an eye on the time of the last tender. Many cruise passengers nevertheless choose not to wander far, and they're not wrong: few neighbourhoods pack so much history into so few streets.

On the way back, the evening light often glides over Wren's façades as the tender returns to the ship. The port call will have shown London at its most maritime: a river that still works, a legendary sailing ship and that invisible line by which the whole world sets its clocks. You go back on board feeling you've held time in your hands.