Fort Davis is 30 miles north of Marfa on Route 67.
Fort Davis National Historic Site, on the north side of town, 432 426 3224. The fort was constructed in 1854 to protect the stagecoach service on the newly opened San Antonio-El Paso road from Apache and Comanche attacks.
The McDonald Observatory is atop Mt. Locke. By day, visitors can tour the telescopes and the planetarium ($8 adult, $7 children), which are owned by the University of Texas. The real attraction, though, are the Star Parties ($10 adult, $8 children) after dusk on Tuesday, Friday and Saturday. (Nov-Mar: 7:30PM, Apr-Aug: 9:30PM, Sep-Oct: 9PM) Two of the observatory's more powerful telescopes - as well as several smaller ones - are set up outside for visitors to catch a startlingly clear glimpse of star clusters, distant galaxies and even a member or two of this solar system. The altitude and the remote location ensures that light pollution is kept to a minimum, and enthusiastic guides are on hand to explain exactly what the scopes are showing. Bring a warm jacket regardless of the season, as the temperature drops rather steeply at night.