Riverside, California is 3.3 times larger than Pomona, California.
Area: 63 km2 calculated
Pomona is the fifth largest city in Los Angeles County, California. Pomona is located in between the Inland Empire and the San Gabriel Valley. As of the 2010 United States Census, the city's population was 149,058. 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