Complex sentence: The Rhine River itself looked different in 1790 than it does today; the passage from Basel to Iffezheim was "corrected" (straightened) between 1817 and 1875, and from 1927 to 1975, a canal was constructed to control the water level.
Split into simpler sentences: The Rhine River itself looked different in the 1790s than it does today; the passage from Basel to Iffezheim was "corrected" (straightened) between 1817 and 1875. Between 1927 and 1975, a canal was constructed to control the water level.