Massive Roman canal discovered

100 yards wide qualifies as massive.
It never ceases to amaze me what hasn’t been excavated that’s sitting right under our noses — but there you have it, resources for digging are finite.

Scholars discovered the 100-yard-wide (90-metre-wide) canal at Portus, the ancient maritime port through which goods from all over the Empire were shipped to Rome for more than 400 years.
The archaeologists, from the universities of Cambridge and Southampton and the British School at Rome, believe the canal connected Portus, on the coast at the mouth of the Tiber, with the nearby river port of Ostia, two miles away.
It would have enabled cargo to be transferred from big ocean-going ships to smaller river vessels and taken up the River Tiber to the docks and warehouses of the imperial capital.

Here’s the excavation website: the Portus Project.
The most fun may be their page on Visualizing Portus – there are some fun animations.