This summer I visited the Lowell Observatory in Flagstaff, Arizona. Sky watchers will love this place! The Lowell Observatory is known as the Home of Pluto because its founder, Percival Lowell, worked with Clyde Tombaugh who discovered Pluto with one of the observatory's telescopes in 1930. (Now Pluto is considered to be a dwarf planet.) If you visit the Lowell Observatory you will see the telescope that was used to discover Pluto.
Ongoing discoveries continue at the Lowell Observatory by current astronomers. Lowell scientists are internationally recognized as experts about every planet, star, and galaxy. I recommend attending presentations in the Lowell Universe Theater. Also, the exhibits are educational and there are hands-on activities for children in the Orbits Curiosity Zone. In addition, visitors can attend stargazing events at night.
The Lowell Observatory is definitely a place one can visit multiple times.