Complex sentence: In 1818 Fowler began work on the new market at Gravesend in Kent, with a pair of colonnades, 80 feet long, connected by a covered building at one end.
Split into simpler sentences: In 1818 Fowler began work on a new market at Gravesend in Kent. It consisted of a pair of colonnades, 80 feet long, connected by a covered building at one end.