Complex sentence: Most towns remained far smaller places, so that in 1500 only some two dozen places in the world contained more than 100,000 inhabitants: as late as 1700 there were fewer than forty, a figure which would rise thereafter to 300 in 1900.
Split into simpler sentences: Most towns remained far smaller, so that in 1500 only some two dozen places in the world contained more than 100,000 inhabitants. As late as 1700, there were fewer than forty, a figure that rose to 300 in 1900.