Complex sentence: It was not until the late 20th century that excavations by Charles Bonnet and the University of Geneva confirmed that this was not the case, instead uncovering a vast independent urban complex that ruled most of the 3rd cataract for centuries.
Split into simpler sentences: It was not until the late 20th century that excavations by Charles Bonnet and the University of Geneva confirmed that this was not the case. They instead uncovered a vast independent urban complex that ruled most of the 3rd cataract for centuries.