At home with Alexander the Great: Ancient Greece's largest palace just reopened after years of painstaking repairs – and we're first through the door

It is an almost unfathomable sensation to stand in the enormous colonnaded courtyard where 4,000 Greeks lived in 336 BC. declared the 20-year-old Alexander king of Macedonia. Especially when you practically have the place to yourself.

Alexander the Great's palace in ancient Aigai, modern Vergina, now welcomes visitors after years of painstaking repairs. I stroll through the empty theater where Alexander's father, Philip II, was murdered by a bodyguard at the wedding of his daughter Cleopatra.

His heartbroken son was crowned shortly afterwards in the vast palace where I stand. At 15,000 square meters, it is the largest surviving building from the classical Greek period.

But because it is located in old-fashioned northern Greece, far from the tourist hotspots of Athens and the holiday islands, it is wonderfully empty.

My only companions are the rows of Doric and Ionic columns, re-erected for the first time in 2,200 years, after the Romans toppled them in the second century BC. Behind me are the snow-capped peaks of the Pierian Mountains. Below me lies the Macedonian plain, with its lattices of peach trees.

The palace, an hour's drive from Thessaloniki, is the largest surviving building from the classical Greek period at 15,000 square meters.

Harry reveals the renovation is 'all part of a campaign to attract tourists to northern Greece'

Alexander the Great (356-323 BC) was Alexander the Great – the most triumphant leader ancient Greece has ever seen. He moved east through modern Turkey and defeated Darius III, king of Persia. He marched into Egypt and even into India, winning every battle. He died, only 32 years old, in Babylon.

Alexander is still hero number one here. His palace was reopened this month by Greek Prime Minister Kyriakos Mitsotakis. In Greece's second largest city, Thessaloniki, an hour's drive from the palace, a mighty statue of Alexander on his beloved horse, Bucephalus, rises over the promenade on the Aegean Sea.

Even at the train station of Thessaloniki, a bronze bust of Alexander takes pride of place. You can see why the Greeks revere the palace today. I wander through dining rooms where Alexander held symposia – drinking parties where they discussed philosophy. He was taught by Aristotle, Greece's best philosopher, and was devoted to Homer's Iliad.

In Thessaloniki, a mighty statue of Alexander on his beloved horse, Bucephalus, rises above the Aegean Sea promenade (above)

Intricate mosaic floors depicting goddesses, flowers and winged creatures have been preserved, as has a shrine dedicated to Heracles, the Greek strong hero, son of Zeus, believed to be Alexander's ancestor. After its destruction by the Romans, the palace became a stone quarry. It was rediscovered in the 1970s, but remained a wreck. In 2007 it was closed for this spectacular renovation.

The palace was largely built by Alexander's father in the mid-4th century BC – and you must see his buried tomb, a five-minute drive away. You descend under a tumulus of earth to reach the grave, which was only discovered in 1977.

Philip's remains and those of one of his queens were found behind a marble door, with his golden crown and golden wreath of oak leaves – the pinnacle of Greek craftsmanship, plus small ivory busts of Philip II and Alexander.

The tomb of Alexander's father Philip II is a five-minute drive from the palace. “You descend under a tumulus of earth to reach the grave, which was only discovered in 1977,” writes Harry

The renovation is all part of a campaign to attract tourists to northern Greece. It's a long time ago. Not only Vergina but also Thessaloniki are home to some of the most beautiful treasures in the world.

Thessaloniki is well equipped with hotels and restaurants. The Excelsior is an elegant, classic hotel, but modern with modest prices.

Thessaloniki was a vital Roman city. The Roman forum has been preserved, as have the 4th century AD walls that encircled the city. Two gigantic buildings from 300 AD. – the Arch of Galerius and the Rotunda – were built in honor of Emperor Galerius (258-311 AD).

These mighty fragments of ancient northern Greece should be much better known, just like the palace of Alexander the Great.