One Piece Grand Line: Where Is The Deadly Ocean?

We've heard mention of the Grand Line in Netflix's One Piece, but where is this line of ocean and why is it so important?

As Gol D. Roger lay dying, he revealed to the world that he had

Found this map somewhere and now I understand Grand Lind/Red Line

One Piece: The powers and abilities of the Sea Kings explained

One Piece World - Our First Post About Grand Line <3 The Grand

10 Things You Didn't Know About One Piece's World Map

How does the world of 'One Piece' anime look like geographically

One Piece's Magic Explained

How in the world did Shanks meet Luffy? On maps, I don't see any

Grand Line, One Piece Wiki

I just learned it is possible to travel through the calm belts

The Grand Line Ocean: A Detailed Explanation in One Piece

Top 10 Worst Islands on the Grand Line