Once on board the riverboat they are met by a Mr. Montero who has hired King and his men to blow up a mission on the Texas / Mexico border where the Mexican army has an arsenal of weapons. King keeps looking at the back of a woman playing the piano across the room from their discussion. He seems to recognize her for some reason. When she’s finished playing, she turns around and it’s Alicia.
The steamboat footage is stock footage while the interiors were filmed on a soundstage in Madrid.
For a more detailed view of this site and other Spaghetti Western locations please visit my friend Yoshi Yasuda’s location site: http://y-yasuda.net/film-location.htm and Captain Douglas Film Locations http://www.western-locations-spain.com/