Ontario (Canada) is 5,163 times larger than Riverside, California.
Ontario is one of the ten provinces of Canada, located in east-central Canada. It is Canada's most populous province by a large margin, accounting for nearly 40% of all Canadians, and is the second largest province in total area. Wikipedia
Area: 208 km2 calculated
Riverside is a city in Riverside County, California, United States, located in the Inland Empire metropolitan area. Riverside is the county seat of the eponymous county and named for its location beside the Santa Ana River. Wikipedia