Rocky Mountain National Park is 5.2 times larger than Boise, Idaho.
Area: 207 km2 calculated
Boise is the capital and most populous city of the U.S. state of Idaho, as well as the county seat of Ada County. Located on the Boise River in southwestern Idaho, the population of Boise at the 2010 Census was 205,671, the 99th largest in the nation. Its estimated population in 2013 was 214,237. Wikipedia
Area: 1,075 km2 calculated
Rocky Mountain National Park is a national park located in the north-central region of the U.S. state of Colorado. Wikipedia