Historic downtown & Route 66
Flagstaff's downtown, straddling the original Route 66 and the BNSF rail line, is the walkable core: brick buildings, coffee shops, outfitters, and the 1927 Hotel Monte Vista as the landmark. Heritage Square hosts events through the year, and trains roll through constantly, part of the charm, and a light sleeper's warning if your hotel is trackside.
Lowell Observatory
Perched on Mars Hill above downtown, this is where Pluto was discovered in 1930. Daytime tours cover the history; the real show is the evening programming, telescope viewing under some of the darkest skies of any city in America. Flagstaff was the world's first designated International Dark Sky City (2001), and it shows. Book evening sessions ahead in busy seasons.
[AFFILIATE: Lowell Observatory tickets]
Arizona Snowbowl & the San Francisco Peaks
Fifteen minutes from downtown, Snowbowl is a ski area in winter and a scenic chairlift/gondola ride in summer and fall, the fall aspen color (late September into October) is one of Arizona's great seasonal sights. The truly ambitious hike Humphreys Peak, Arizona's highest point at 12,633 feet, from the Snowbowl trailhead: a full, serious day, summer only.