Il porto marittimo di Porto Flavia, costruito nel 1924. Sulcis-Iglesiense, Sardegna, Italia

But it’s not reaching the sea. Can it still be called an harbour?

Pic of how this worked: https://mybestplace.com/uploads/2018/09/Porto-Flavia-Sardegna-Italia-2.jpg

from here: https://mybestplace.com/en/article/porto-flavia-an-ingenious-work-with-a-breathtaking-view

At first I thought the picture was AI generated, but apparently not. Interesting place, added to the ‘want to visit eventually’ list.