Complex sentence: Barnett is credited for having built the first substantial building in the area now known as Queen Victoria Park, erecting his first museum in 1827 near the base of the Canadian Horseshoe Falls.
Split into simpler sentences: Barnett is credited for having built the first substantial building in the area now known as Queen Victoria Park. He also erected his first museum in 1827 near the base of the Canadian Horseshoe Falls.