The causeway formed a barrier further separating the two harbours of Alexandria's oceanfront. This arrangement had the advantage of protecting the harbours from the force of the strong westerly coastal current. The east side of the mole became the Portus Magnus (the Great Harbour or Royal Harbour), now an open bay.
The causeway served as a barrier, further isolating the two harbours of Alexandria's oceanfront. This setup provided protection for the harbours from the strong westerly coastal current. The eastern side of the mole was designated as Portus Magnus (the Great Harbour or Royal Harbour), now an open bay.