Europe is a continent of coasts. Indented and irregular, its serpentine shores stretch almost 24,000 miles, though they’re shrinking, and shrinking quickly. Across Europe, seas are rising at an average rate of around 2 to 4 millimeters per year. And though that may sound small, that rate is far from insignificant, threatening to swallow up Europe’s low-lying costal cities, like Venice and Amsterdam.

Though the current threat to the coastal communities of Europe is unprecedented — and undeniably connected to human-caused climate change — surging seas aren’t a completely modern concern. Over the centuries and the millennia past, the tides have taken a number of ancient cities, or parts of ancient cities, in and around Europe, thanks to earthquakes, tsunamis, and other natural disasters.

Plumbed by underwater archaeologists, submerged sites like Pavlopetri and Heracleion serve as a climate change warning, as well as a treasure trove for all sorts of strange and spectacular insights into the world of antiquity. Here are a few lesser-known sunken cities, whose secrets are just starting to surface.

Read More: Stop Searching For Atlantis And Find These 4 Ancient Underwater Cities Instead

1. Akra

What Is the Greek City of Akra?

Greek influence stretched far outside the current borders of Greece for a broad span of antiquity. The Greek city of Akra sat on the north side of the Black Sea, in the Kerch Strait off the coast of the Crimean Peninsula. Founded in the 6th century B.C.E., the city was part of what was called the Kingdom of Bosporus, a colonial state of ancient Greece.

When Was the Sunken City of Akra Dicovered?

Remains of the sunken city of Akra were discovered in the 1980s, according to the Russian Geological Society. The city enjoyed trade from both land and sea due to its excellent location on the strait. But the waters of the Black Sea rose in the 3rd century B.C.E., causing many residents to abandon the area. By the 4th century C.E., the city was mostly underwater.

2. Simena

Where Is the Sunken City of Simena?

The sunken city of Simena is part of the ancient region of Lycia which now sits on the coast of southwestern Turkey.

Why Did Kekova Sink?

An earthquake in the 2nd century C.E. caused the area of Kevlova to sink below sea level. This town, and a few others in the area, was part of the Lycian League, a democratic alliance of independent Mediterranean city-states formed in the 1st century B.C.E. Today, the area of Kekova is under review by UNESCO for listing as a World Heritage site.

Read More: 5 Ancient Societies that Collapsed When the Water Ran Dry

3. Agios Petros

When Was the Sunken City of Pavlopetri Discovered?

In 1967, underwater archaeologist Nicholas Flemming discovered the Greek city of Pavlopetri, which was first occupied around 5,000 years ago off the coast of southern Laconia in the Peloponnese. Fourteen years later, in 1981, the University of Southampton archaeologist found another sunken settlement, this time many years older.

Where Is the City of Agios Petros?

The city of Agios Petros sits on the coast of the Aegean Islands near its namesake islet — a place where farmers and fishers settled sometime before 6000 B.C.E. Research at this ancient site is ongoing, being led by Nikos Efstratiou, an archeologist at Aristotle University of Thessaloniki.

So far, researchers have found sea walls and several structures that may be houses. Earlier expeditions have also found artifacts inlcuding animal bones, stone tools, and ceramics.

Read More: Which Ancient City Is Considered the Oldest in the World?

4. Canopus

What Is the Egyptian City of Heracleion Known For?

The Egyptian city of Heracleion receives a lot of attention. Founded in the 8th century B.C.E., the city is famed for its temples, which remain — in ruins — in the waters of the Mediterranean. This year, for instance, researchers found a temple for the god Amun amongst Heracleion’s remnants, replete with gold trinkets and other treasures. But less attention is paid to the city’s neighbor, Canopus, submerged on the western part of the Nile Delta.

What Happened to the Sunken City of Canopus?

The ruins of Canopus suggest that the site boasted wonderful structures as well, including sanctuaries for the gods Osiris and Serapis. In later times, the Roman Emperor Hadrian enjoyed a visit to Canopus so much that he had a replica of some of its buildings made in Rome, according to Franck Goddio, the archaeologist who discovered Canopus’s remains about two decades ago. By the 8th century C.E., however, rising sea levels, earthquakes, and tsunamis had leveled both Canopus and Heracleion, sending the cities into the sea.

5. Rungholt

What Is the Lost City of Rungholt?

What the legendary city of Atlantis is to the Mediterranean, Rungholt is to the North Sea. A center for trade, the city was overwhelmed by a powerful storm surge in 1362 known as “The Great Drowning of Men.” In fact, legends have long held that this lost settlement was plunged into the ocean as a punishment for its inhabitants. But the precise location of the city was long unknown — until now.

When Was Rungholt Discovered?

In 2023, researchers found submerged ruins that were likely associated with Rungholt. The ruins were Frisian, built by a group of Germanic-speaking people from the coasts of what is now Germany and the Netherlands in the 12th century C.E. The remains of a large church were discovered at the site, in the mud flats around Hallig Südfall Island in the midst of the Wadden Sea.

Read More: 5 Ancient Cities That No Longer Exist