If time permits, and you don't mind watching a movie on your vacation, consider a visit to West Wind Drive-in; especially if visiting from out of the country where drive-ins are infrequent. And for an added bonus; it's normally a double-feature, so you get two movies for the price of one.
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North Las Vegas Golf Course
Golf and disc golf.
Skate and BMX park, sports fields and dog park. Includes the AMP, an outdoor amphitheater/ concert venue.
CSN Planetarium
It's not on par with L.A.'s Griffith Observatory or Chicago's Adler Planetarium, but this planetarium and observatory can still help give an understanding to the skies and open space beyond. There's also an adjacent astronomy store that's open during the show times. Be aware, however, that chairs do not lean back, so there is a lot of looking up on your part.
A pleasant oasis with ponds and tules and also the Tules Spring Ranch with some roaming peacocks and Pleistocene fossil exhibits.
Home base of the air demonstration squadron United States Air Force Thunderbirds among others, the base is open to the public during airshows. Other than that, you can see military aircraft taking off and landing from a distance.