Complex sentence: Around 1800 the tea rooms were developed into a larger building which became known as the Hornsey Wood House/Tavern, and a lake was built on the top of the knoll with water pumped up from the nearby New River.
Split into simpler sentences: Around 1800 the tea rooms were developed into a larger building which became known as the Hornsey Wood House/Tavern. A lake was also built on the top of the knoll with water pumped up from the nearby New River.