Depends on what you mean by "big", as well as by "city". The biggest city proper, other than NY, in the NY-NJ-CT tristate is Newark, NJ (275,000), about 25 mi west of NY. As far as other large metros go, Philadelphia is about 90 mi to the south west (pop ~6,000,000) while Hartford (1,200,000 or about the size of Buffalo) , Providence (1,500,000) and Boston (5,500,000) are about 100, 150, & 200 mi, respectively, to the Northeast.
Denver and Colorado Springs.
Denver
Denver Colorado
Denver and Colorado Springs.
Denver, Colorado Springs, and Pueblo
Just one, Denver.
Denver, Colorado Springs, and Aurora.
The 5 largest cities in Colorado by population are Denver, Colorado Springs, Aurora, Fort Collins, and Lakewood. Denver has a population of 600,158. Colorado Springs has 416,427. Aurora has 325,078. Fort Collins has 143,986. Lakewood has 142,980
They are the most populated Colorado cities.
Consider Denver.
Denver International Airport - Denver, CO (DEN / KDEN).
The closest international or regional airport is Denver International Airport (DIA).