Complex sentence: Between 400 and 450, the population was estimated at around six-hundred people; this rose to a peak of twenty-eight thousand between 750 and 800-larger than London or Paris at the time.
Split into simpler sentences: Between 400 and 450 AD, the population was estimated at around six-hundred people. This rose to a peak of twenty-eight thousand between 750 and 800 AD-larger than London or Paris at the time.