[sampo]

There is also 2022 Netflix series "Ancient Apocalypse", presenting a theory that there was a civilization (not industrial, but like Romans or Egyptians) living on the coastal areas during last ice age, but their traces have disappeared now that sea level is 120 meters higher than during ice age.

https://en.wikipedia.org/wiki/Ancient_Apocalypse

[shantara]

In the same vein, I’ve heard historians theorize that Doggerland was the most comfortable area for human habitation in Northern Europe during its existence, with its lowlands, lakes and river systems perfectly matching the landscape of the other ancient civilization centers. The lands of the modern UK and Scandinavia were by comparison inhospitable highlands, where humans have moved after their ancestral lands were flooded.

See https://en.wikipedia.org/wiki/Doggerland and the episode of BBC In Our Time podcast on the subject.

[BitwiseFool]

I haven't seen the show, but I'm captivated by the idea that there are probably thousands of submerged sites like Cosquer Cave that hold traces of human history that are lost to both time and the sea. It's not on the same level as a city, but I am intrigued by it's existence nonetheless. It is also somber to think about how much artwork in that cave was washed away when it was flooded.

https://en.wikipedia.org/wiki/Cosquer_Cave