Serdica (Serdika) The Lost City Discovered Under Modern Sofia

Was Serdica a real city, or a mystery like Atlantis?

Serdica (Serdika) was very real, and even pre-dates the Romans!

Here is everything you need to know about the lost city, including what you can see today.

A picture of Roman architecture in a foggy sunrise. What Serdica may have looked like in the 3rd and 4th centuries.
What Serdica may have looked like.

What is Serdica?

Serdica (or Serdika) was the name given to the city of Sofia, Bulgaria, in ancient times.

The city is often referred to as a Roman city, and those are the ruins that have been found, but it was actually named after a Celtic tribe called “Serdi“.

Pin reads "Ancient Sofia Serdica" Over a background of ancient Roman Ruins of serdica with Roman coins beside text.

This name stuck for nearly a millennia, and the city became an important part of Euopean history.

Ancient History of Serdica

Bulgaria is one of the oldest countries in Europe, and the site of Serdica (modern day Sofia) was inhabited as early as 6,000 BC. The remains of a few different neolithic settlements from a broad range of time periods (6000 to 3000 BC) were found here.

Earliest Known Rulers

The Thracians settled the area around 500 BC, but were conquered in 339 by Philip II of Macedon.

(The same Philip II that took Plovdiv, and named it Philipoppolis back in the day.)

A sepia portrait of Philip II of Macedon who took Serdica from the Serdi people

Becoming Serdica

Finally the city gained it’s first known name when the Celtic tribe Serdi took the city and renamed it, sometime between 300 BC and 29 BC.

The earliest reference to the Serdi is in 29 BC when they were documented as having attacked a Roman general while he was on a journey.

However Celtic artifacts found in the area prove that the occupation began much earlier.

Roman Occupation of Serdica

The story goes that the same Roman general – M. Licinius Crassus – who was attacked by the Serdi, returned the next year with an army to punish them, and thus began the Roman rule of Serdica.

Serdica became a very important and central city in the Roman Empire.

Under the rule of the Emperor Diocletian, the city became the capital of the province Dacia Mediterranea.

A bust statue of the Emperor Diocletian who ruled Serdica, in front of a stone wall.

It is even said that Constantine the Great considered making Serdica the capital of the empire before ultimately choosing Constantinople.

Serdica continued expanding, and remained a strong part of the now Eastern Roman Empire (Byzantine Empire) until it was destroyed by the Huns in 447.

The city was rebuilt in the 500’s by the Byzantine ruler Justinian.

The wikipedia page states that Serdica was renamed at this time to Triaditsa, but I don’t think that’s correct.

This Britannica article indicates that the city was renamed Sredets in 809 when it was taken by Bulgars.

The name Sredets is a Bulgarian name, and it is translated to Triaditsa in Greek.

It makes more sense that Serdica was renamed under Bulgarian rule, and not changed to the Greek/Bulgarian name Triaditsa/Sredets while still a Roman city.

How Was Serdica Lost?

Map of Ancient Rome including Thrace and Serdica

After Serdica was destroyed by Huns it was essentially built over top of by the next dynasties.

This was commonplace in ancient times, to level things off and start again, rather than haul everything away.

When Were Remains of Serdica First Discovered?

Modern historians started speculating that an amphitheatre existed somewhere under Sofia in 1919, when a stone plate from Roman times was found depicting gladiators fighting wild animals.

The first ruins were discovered in 2004 while building a hotel. These were the ruins of the amphitheatre.

Rather than, you know, look for the rest of it, life in the city continued as usual.

More ruins sprung up quite unexpectedly in 2006 when digging the foundation for a neighbouring building. Ah Bulgaria.

If you were wondering, they still built the hotel. The ruins are proudly displayed in the lobby. (More on that in a moment.)

Ruins outside at the Serdica Ancient Complex beside the Serdika II metro station

More ruins of Serdica were discovered in 2010 during the construction of a metro tunnel and station.

Visiting Ruins of Serdica Today

If you visit the town of Sofia Bulgaria today, you can marvel at a decent amount of ancient Serdica.

Here are the sights that have been uncovered so far:

Ancient Serdica Complex

The complex at Sofia’s Metro station Serdika II is the largest area of ruins in the city. There is a large open air complex beside the street, and the sidewalk above leads past the entire length of the area.


Between this outdoor area and the areas inside, is the remnants of 8 streets, a church, Roman baths, and houses.

You can even eat at a restaurant overlooking ancient Serdica.


More of the ancient complex is on display inside the Serdika II Metro Station.


Collage of two polaroid photos of the ruins inside Serdika II Metro station in Sofia, with ancient coins scattered around the photos.

In addition to these preserved ruins, the metro station displays a variety of sculptures, tablets, and other artifacts at the platform level, in glass display cases.

Eastern and Western Gates of Serdica

Still inside the metro station, there is an underpass beneath the road that passes by the “Eastern Gate.”

A view in the metro system of the Eastern Gate of Ancient Serdica in Sofia Bulgaria
Ann WuytsCC BY 2.0, via Wikimedia Commons

The ruins of the “Western Gate” are outdoors with the rest of the complex. Not much of it is left.

Serdica Bridge

There are the remains of a Roman bridge that would have crossed the Vladaya River, near modern day “Lion’s Bridge,” but that is little more than a large pile of rocks.

Serdica Amphitheatre

Remember the hotel I mentioned that was built over the amphitheatre?

That is Arena di Serdica Hotel, and you can stay there for about $160 USD per night.

You can also visit the ruins in the hotel for free, if you don’t want to splash out on what is a very expensive hotel by Bulgarian standards.

I do think one night may be worth it, in the spirit of Slow Travel and wanting to soak up the atmosphere.


Church of St. George

The Church of St. George, or St. George Rotunda, is an ancient church in the heart of Sofia (nee Serdica).

The church was originally built in the 4th century as Roman baths.

During the time that Serdica was the capital of Dacia Mediterranea, is when it is thought to have become a church.

An ancient brick domed roof church in front of an 18th century building with 3rd century ruins in the foreground from early Serdica. St. George Church Rotunda Sofia

Some of the ruins in front of the church date back to the 3rd century.

Between the 10th and 14th century, many frescoes were added to the interior of the church, but the oldest remaining are from the 4th century.

St. George Church is on the list of the world’s oldest churches.

Entrance is free.

St. Sophia Basilica Necropolis

Although the original church of St. Sophia was ancient, it was destroyed repeatedly through the centuries. The current structure is partially from the 6th century, and the rest is from the 16th and 19th centuries.

The necropolis under St. Sophia however, dates back to the Serdica era.

This ancient graveyard was built in the 4th century, supposedly over top of a 2nd century theatre.

Admission to the crypt is 6 Lev (~$3.50 USD)


Map of Serdica Ruins

Here are the locations of all the documented ruins found in Sofia so far.

Thanks so much to Roamin the Empire for creating this map!


Is There More Serdica to Discover?

The big question remains: Will we find more of ancient Serdica?

Undoubtedly there are more ruins hidden under this city of secrets, but nobody is about to go looking for them.

It’s totally understandable that there are no plans to dig up the whole of Sofia, but you have to wonder how many ruins may have been discovered in past decades and they were just quietly built over top of.

Pin of St. George Rotunda Church Serdica. Text reads: Discover Ancient Sofia

It seems unlikely that the first anyone has dug in central Sofia was in the early 2000’s.

Seeing how much has been revealed and preserved in the last 20 years, hints that there could be much more to come!

Other Historical Sites in Bulgaria

Bulgaria is truly an amazing country FULL of historical sights that you have never heard of.

If you want to see more evidence of ancient Romans in Bulgaria, make the short drive to Plovdiv and take in their very own amphitheatre and stadium.

A side angle of the Plovdiv Amphitheatre in Bulgaria, also known as the ancient theatre of Philippopolis, capturing the full stage area

Aladzha Monastery is a medieval rock monastery near Varna, close to the Black Sea.

The Rock-Hewn Churches of Ivanovo are a similar site to Aladzha on a much larger scale. These are located near the town of Ruse, close to the Romanian border.

Want More?

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