If you've built a canal big enough to carry boats, and suddenly arrive at a valley, then you can build a bridge with a trough on top to let the water continue. And that's a viaduct.
Pretty much the same thing, but too narrow to carry anything but a channel of water, and it's an aqueduct.
viaduct
There are several, but the most famous one is the Pontsticill Aqueduct on the Llangollen Canal in North Wales. It was built by Thomas Telford between 1796 and 1801 entirely from iron, and towers on eight massive pillars 126 feet above the River Dee. Next to it lies the Chirk railway viaduct.
Glenfinnan Viaduct isn't a person. It's a railway viaduct located in the Scottish highlands.
In simple terms it is a canal that crosses a purposely built bridge, like a viaduct, or a canal that has sections built for specifically transporting the water. All canals are in effect aqueduct canals because they are usually completely man-made and have the purpose of transporting, channelling or redirecting water, although we usually associate canals with modes of transport for barges.
An aqueduct delivers water from one place to another by a pipe dug under the ground, while a n aquifer is a layer of rocks underground.
Cadishead Viaduct was created in 1893.
Garabit viaduct was created in 1885.
Starrucca Viaduct was created in 1848.
Altenbeken Viaduct was created in 1853.
Huckford Viaduct was created in 1902.
Jezerane Viaduct was created in 2004.
Caracău Viaduct was created in 1897.