Originally the carriage house for the Mexico Point Club, this building housed the horses and carriages that brought guests from the train station. In the 1920s and 30s, after the park switched to motorized vehicles, Columbia University professor William Casey obtained permission to transform it into a medieval manor house. Popular with his students, Casey invited several of them each summer to Mexico Point, where they enjoyed the setting and in return worked on the interior artwork. They carved and painted figures designed by Severin Bishof and often added designs of their own, leaving decorations throughout the cottage that reflect many artists working together in comradeship and appreciation for the period they were depicting. Casey and his friend Bishof also altered the structure itself, building a moat-like defensive feature around two sides with narrow windows shaped like openings for crossbows, but fitted with stained glass to create beauty as well as a medieval effect. The original glass was set with a tar-like material that later became brittle, and new stained-glass windows were created in 2020 as a community project financed by the Shineman Foundation, with 18 windows designed by people ages 6 to 86 from Oswego to Pulaski. The ceiling beams bear a Latin quotation by Cicero near the fireplace and a longer one by Chaucer, with some inserted names thought to be those of students and perhaps their girlfriends. Casey and Bishof also built a fireplace from lake-weathered shore stones, using hollow stone chambers beside the firebox and chimney to draw in cold air, warm it, and return it to the room, producing twice as much heat as a traditional fireplace in a design called a heatilator. Bishof, an artist trained in Germany as a wood carver and then a teacher in the Art Department at Syracuse University, designed the medieval figures on the walls after Casey explained his vision. He drew people from every walk of life in that era, including bishops, kings, court musicians, knights, ladies, and both young and old people, while coats of arms above doorways and heraldic symbols carved into floors and doors completed the decoration of nearly every surface.