Complex sentence: Bath is a city in Somerset, in the south west of England in which, through architecture, all significant stages of the history of England are represented, from the Roman Baths (including their significant Celtic presence), to the present day.
Split into simpler sentences: Bath is a city in Somerset, in the south west of England. All significant stages of the history of England are represented within the city, from the Roman Baths (including their significant Celtic presence), to the present day.