Well, it is great to see that so many of you got this one right.
It is Lago di Traiano, the old harbor of Rome, built by emperor Trajan in the year 103 AD.
The purpose of its hexagonal shape was probably to reduce the waves.
Those who know their classics:
- Walter_V_R
- Paul Franson
- Emil Schierle
- ACG
- hhgygy
- mccrumplair
- steven simmons
- Sandworm
- mehmet durmus
- Farceur
- Adam Macer
- Ernesto Posse
- Noisette
- steve willis
- Keith
- CuriousJM
- Dana Payton
- Paul Voestermans
- mehtab sond
- Sarah G.
- Gordon Silliker
- quiltadel
- TitouPinkRider
- Graham Foxall
- rob de wolff
- a11c
- Sasha Smith
- Rosella
– Hint –
- Gillian B
- Ivar Bonsaksen
- Pascal Gilbraith
- Shelly
- Denniz P
- krenek
- Mik
Well it wasn’t hard to get!. I punched ‘hexagonal lake’ onto Google Images and I had it in seconds..