Numismatic Museum of Athens

Step off the traffic of Panepistimiou Street and the noise drops away. The air under the arched loggia is cooler. Overhead, painted ceilings glow in soft reds and blues, and the stone underfoot is smooth from more than a century of footsteps. You are standing in a private house built to look like a palace. Today it holds one of the oldest public collections in Greece... a museum devoted entirely to money.

First, the building. This mansion is called Iliou Melathron, which means the Palace of Ilion. Ilion is the ancient Greek name for Troy. The name tells you exactly who lived here. This was the Athens home of Heinrich Schliemann, the German businessman turned archaeologist who excavated the site he believed was Troy. He and his Greek wife, Sophia, built the house in the late nineteenth century, at the height of his fame.

The architect was Ernst Ziller, a Saxon-born designer who shaped much of nineteenth-century Athens. Ziller gave Schliemann a building in the Renaissance revival style, with an open arcade on two levels facing the street. From the pavement it looks calm and orderly. Inside, the mood changes. Schliemann wanted a house that told the story of his discoveries, and he filled it with images and words from the ancient world.

Here is the first detail most visitors miss. Look up at the walls and ceilings and you will find painted inscriptions in ancient Greek. Many are lines and phrases chosen by Schliemann himself, drawn from classical literature. He read Homer obsessively, and he wanted Homer's world around him at home. The painted decoration, much of it by the Slovenian artist Jurij Šubic, mixes ancient motifs, small figures and scenes inspired by Pompeii, the Roman town buried by Vesuvius.

Now look down. The floors are laid with mosaics, and many of them carry patterns and motifs connected to the objects Schliemann found in the ground. Visitors often walk straight across them while looking at the glass cases. Take a moment to stop. The house itself is part of the exhibit, and in some rooms the floor is as interesting as anything behind glass.

Schliemann did not live here for very long. He died in 1890, and his family later sold the house. The Greek state acquired it in the twentieth century, and for decades it served as home to some of the country's highest courts. Judges and lawyers worked in rooms that had been built for a family that named its children Andromache and Agamemnon, after heroes of the Trojan War.

The Numismatic Museum moved into the mansion in the late 1990s. The collection is much older than its present home. It was founded in the 1830s, in the first years of the modern Greek state, when the young country was building its institutions almost from nothing. Coins were among the first things it set out to protect. Small, durable and often stamped with names and faces, they are some of the most reliable witnesses to the ancient past.

The collection is enormous, numbering in the hundreds of thousands of objects. Only a fraction is on display at any one time. Alongside coins you will find weights, seals, medals, engraved gems and other tools of trade and authority. Together they follow money in this part of the world from the first Greek coins, through the Roman and Byzantine centuries, into the medieval period and the modern Greek state.

Here is the second surprise. Coinage is a fairly recent invention in human history. Before coins, people traded with lumps of metal measured by weight, or exchanged goods directly. The idea of a small, standard piece of metal stamped by an authority took hold in the region of Asia Minor, in what is now western Turkey. Greek cities picked it up quickly, and each city put its own symbol on its coins.

The coin you will probably recognise is the Athenian silver tetradrachm, a four-drachma piece. On one side is the head of Athena, the city's goddess, wearing a helmet. On the other is her owl, with large round eyes, beside a small olive sprig and the first letters of the city's name. Athens made these coins in great numbers from its silver mines, and they travelled far beyond Greece. The same owl appears on the modern Greek one-euro coin.

As you move through the rooms, notice how the images change. Greek coins often show gods, animals and local symbols. Roman coins show emperors in profile, a clear statement of who was in charge. Byzantine coins, from the Eastern Roman Empire centred on Constantinople, become flatter and more religious, with Christ and the saints. The coins work like a small, portable history of power, belief and art.

Bring patience to the cases. Many of these objects are tiny, smaller than a fingernail, and the best details only appear when you lean close. Look at the edges, the small letters and the marks left by the dies that struck them. Some coins are slightly off-centre, which shows that each was struck by hand. Every one of them passed through real hands, in real markets, buying bread or paying soldiers.

When you are ready for a break, the mansion has a garden at the back with a café. It is one of the quietest spots in central Athens. You can sit among the trees and look at the rear of the house, where the scale of Schliemann's ambition is easy to see. It is a good place to slow down after an hour of looking at small things.

Before you leave, stand once more in the loggia and look out at the street. Cars and buses pass where Schliemann's carriages once stood. Then check the change in your pocket. If you have a Greek euro, turn it over. Athena's owl is still there, looking back at you, after roughly two and a half thousand years.