I have a little surprise for you,” says Yulieth Saad, my guide in Athens, as she walks me down the steps of the neo-classical metro station of Monastiraki. “You call this a metro station?” I gasp, as I take in the gleaming granite floors and marble walls, piped music, plasma screens and high-tech ticket machines.

“That’s not all,” she says with a smug look, as she leads me to a corner. Here, in a specially-formed space encased with stones, are the remains of Eridanos, an ancient underground river that rose in the foothills of Lykebettos. The Eridanos was found during excavations, under a stone vault dating back to Emperor Hadrian’s time, during which it was turned into a sewer. To come across a long-lost river in the premises of a modern subway station — after centuries — is enchanting!

The construction of the Athens Metro began in the 1990s - it took several years to complete, and cost over $2 billion. Digging in a city with more than 6,000 years of history buried underneath proved to be a challenging task. Engineers from the Metro project, and archaeologists from the Ministry of Culture co-operated in the venture. They pored over ancient texts, and used geo-radar techniques to plot images underground, and pinpoint locations where man-made objects existed.

Five of the metro stations were in the shadow of the Acropolis, and were thought to be high-risk areas. Hence, major excavations were performed before commencing construction. Some stations were built using underground tunnels, boring through solid rock, to ensure that cultural treasures were not disturbed. The locals say that the giant ‘metro rat’ (as they called the tunnel machine) dug into the city’s past, to build its future.

Digging through the layers, the engineers often had to put away the power tools and call in the archaeologists with their brushes. They salvaged and categorised remarkable finds — remains of ancient homes, markets and temples, and even a marble statue of Goddess Athena! As they dug further, public baths, aqueducts, cisterns, myriad graves and cemeteries, and more than 50,000 artefacts emerged. Excavations for ventilation shafts revealed a huge Roman bath, and an early Roman cemetery. From a large sarcophagus to a Roman drain, the construction of the Athens Metro gave the city’s residents an insight into the topography of this great city over the ages.

Many of the historic finds are now housed in local museums. The best artefacts are displayed in the respective metro stations themselves, giving rise to ‘mini museums’. Today, seasoned commuters nonchalantly walk past the treasures displayed in the stations – they are probably used to living in a city where modernity and history co-exist in surreal harmony. Besides the display of ancient finds, contemporary art is also showcased. Greek artists have also re-created ancient stories in modern media in these spaces.

Many of the gleaming stations are offshoots of the Olympics-funded transformations, and are showpieces in their own right — glass lifts transport the elderly and disabled, walls are clean of graffiti, there are no beggars lingering around, and there are strict rules banning food and drink in the stations. My guide tells me that announcements are made in five languages if the authorities see anyone eating or drinking in the stations — all the better to drill the message in!

In the Monastiraki station, near an ancient library from the time of Emperor Hadrian, remains of settlements from 8th Century BC to the 19th century are displayed under a glass platform. At the upper concourse hall of the Syntagma station, below the Parliament Square, artefacts from different periods of Greek history, ranging from pre-historic and Byzantine to classical, are housed in huge glass cases. There are clay pipes, huge urns, ancient roads, mosaics from the 5th Century BC, and gravestones. We can also see a geological cross-section on the wall — a 42-metre stratigraph, which showcases the different layers as they were found, corresponding to a historic timeline. There is a grave from the 4th Century BC (complete with a skeleton), a few metres below a 16th century cistern. At the Acropoli Station, we can see an ancient mosaic floor, oil lamps with images from the 6th Century BC, old clay cups, and plaster casts of figures from the pediments of the Parthenon.

As they say, it is not the destination, but the journey that counts. So, if you are in Athens, get a Metro day pass (€4) and go on a truly historic ride - before you catch the train to your next destination!