The fort's walls and crenelations are clearly visible throughout the episode. The fort set plays a major role in Bonanza: Alias Joe Cartwright (1964).
In some shots Vasquez Rocks can be seen from the set in 'Arena' itself. This set was directly adjacent to Vasquez Rocks - so close that in Bat Masterson: Dagger Dance (1961), both the fort and the distinctive peaks of Vasquez Rocks appear in the same shot. It also is an important part of the coincidentally-titled Mission: Impossible: Trek (1967).
The fort set (Cestus III), retouched here with science-fiction trappings and location signs, can be seen in several early episodes of The Wild Wild West, most prominently in The Wild Wild West: The Night of the Sudden Plague (1966).