They say the world is round, but I am flat. What am I?

A story passed down through the ages, a fabled city lost in all but tale. These people grew greedy, attacked the Athenians, and overnight their home was gone. Many fables have existed, about what advancements existed, but no proof has ever been found.

Where land and sea share a lazy embrace, waves gently dance in a tranquil space. A boundary of blue, where horizons blend, stretching endlessly, where journeys end.

I rise and fall as boats stall over mountain ridges and trolls fidges stone by stone built up in rome just to fall back down in london

Red lines cross on blue, framed in white. Built from older flags, stitched into one. Raised on ships and over castles. Say 'together' first, then a common bird, then captain’s first name.