Cite

[Courtyard of castle, showing Conrad under the giant helmet] [art original].

MLA

[Courtyard of Castle, Showing Conrad under the Giant Helmet] [Art Original]. 0AD. https://collections.library.yale.edu/catalog/16704395.

APA, 6th edition

[Courtyard of castle, showing Conrad under the giant helmet] [art original]. (0 C.E.). [Illustrations, Watercolors British 19th century]. https://collections.library.yale.edu/catalog/16704395.