Director: Henry Hathaway
Cinematography: Jack Cardiff
Art Direction: Alfred Ybarra
Manager of art department: Italo Tomassi
Matte paintings: Unknown
That adventure- romance flick was an independent movie produced by Dear Film Productions, Rome, Italy, and Batjac Productions
That was an independent film production company founded by John Wayne in the early 1950s as a vehicle for Wayne to produce as well as star in movies. It was released by United Artist and filmed at Libya and Cinecitta, Rome.
The matte paintings are uncredited , in fact there is not credit for any kind of special effects, photographic, optical or whatever. It is clearly showed on the film that the matte paintings were added on postproduction.
That could have been done in Cinecitta by matte painter Joseph Natanson, who at that time, was providing mattes for Italian films, by I doubt it. It could be also handled at London by any of the matte painting departments on Pinewood, or Shepperton Studios or it could be also managed at Hollywood by any of the numerous matte departments over there. whoever did that matte work, he did it brilliantly.