It is the year 900, in the early months of spring. A clinker-built longship lies ready at the head of a deep Norwegian fjord, its striped sail furled against the mast, its crew of thirty men preparing to row out on a long crossing of the northern seas. The voyage ahead will last many days, through waters they know only by the memory of those who have returned.

You are standing on the bank of the Eurotas river, where the water runs clear and cold from the Taygetus mountains. It is the year 450 BCE. The morning sun has risen over a city that has never known defensive walls, where low houses of sun-baked brick cluster along the river plain, and the smoke of breakfast fires drifts thin across the olive groves. Men are already walking toward their common mess halls, carrying the prescribed contribution of barley meal and wine.

It is the year 584 BCE, the twenty-first year of King Nebuchadnezzar II's reign. You stand upon the western bank of the Euphrates, where the river bends through the heart of Babylon, greatest city of its age. Behind you rise walls of baked brick so broad that chariots pass upon their summits four abreast, and beyond them the blue-glazed towers of the Ishtar Gate catch the last light of a Mesopotamian afternoon.

It is the year 48 before the Common Era. In the royal palace on the harbour's edge, Cleopatra VII has just been driven from her throne by the ministers of her younger brother. She will soon return, carried in secret through the harbour mouth, past the great lighthouse on the island of Pharos, its fire burning at the entrance to the greatest city the Hellenistic world has ever built. Alexandria already holds more than half a million souls. Its streets run straight as arrows, its library holds the collected learning of centuries, and its ships carry Egyptian grain to feed the Roman republic. Yet the kingdom is three centuries old now, and the shadow of Rome falls longer each year across the harbour.

In the year 682, a king named Jasaw Chan K'awiil I took the throne of Tikal, a city of limestone and plaster rising from the rainforest of northern Guatemala. His coronation marked the beginning of a second golden age for one of the greatest cities of the Maya world, a place where temple-pyramids would soon pierce the canopy above the Petén. The dry season had begun, and the white plazas caught the morning light as workers prepared the foundations of what would become Temple I, the king's eventual resting place.

It is the year 850, in the Benedictine abbey of Lorsch on the Bergstrasse. A monk rises in the darkness before dawn, his breath visible in the unheated cell. The bell for Matins will sound soon, summoning him to the church of St. Nazarius, founded eighty-six years earlier in the time of Charlemagne. The day ahead will unfold according to the Rule of St. Benedict, measured in seven canonical hours, from this darkness until the Great Silence falls after Compline.

The morning light comes early over Mount Hymettus, catching the dust that rises from the Agora where fish-sellers are already laying out their catch. It is the spring of 438 BCE in Athens, and the city has been rebuilding itself for nearly a generation since the Persian fires of 480 BCE. On the Acropolis above, the Parthenon stands nearly complete, its freshly painted marble gleaming pale gold in the dawn, visible from ships approaching the harbour at Piraeus seven kilometres away.

The Sapa Inka Pachacútec Yupanqui has just died after thirty-three years of rule, and his body lies in state in the Coricancha, the temple whose interior walls are lined with beaten gold. The city of Cusco sits at 3,416 meters in the Andean highlands, the administrative, political and military center of an empire that now stretches across 950,000 square kilometers. From here, four roads lead outward to the four suyu, the quarters of the world. Relay runners carry news of the king's death along stone-paved highways that reach from Quito to Santiago, from the Pacific coast to the Amazon basin. It is the height of Tawantinsuyu, the empire of the four parts, and the machinery of its daily life continues without pause.

The galleys are coming home. It is April of 1204, and the lagoon is thick with smoke from cook-fires on the Lido. Doge Enrico Dandolo's fleet has been gone two years. Now the hulls ride low in the water, laden with bronze horses and broken columns from the Hippodrome, with sacks of coins and relics wrapped in silk. The men who walk down the gangplanks will tell stories of a city set on fire, but tonight in Venice there is only the splash of oars and the calling of names across the dark water.

The second battle of Panipat is about to begin. Hemu, the Hindu general who has captured Delhi and Agra, commands a force of war elephants and Afghan cavalry. Fourteen-year-old Akbar watches from a distance as his regent Bairam Khan directs the Mughal army. The mist hangs low over the flat fields where Babur, Akbar's grandfather, had won an empire thirty years before.