The artist often worked with chalk and ink to capture the scale of Roman architecture. His views of the Baths of Caracalla use heavy foreground elements to create a sense of depth. Du Gardijn also documented foreign figures, such as Turkish soldiers around a campfire, with a directness that avoids excessive ornamentation. He prioritised clear lines and structural accuracy. This method makes his depictions of ruins feel grounded and observant.

Modern collectors value Du Gardijn for his architectural precision and his ability to document historical moments. His work fits well in contemporary spaces that favour clean lines and historical curiosity. The sketches of galleys and ruins offer a window into the Mediterranean through a Dutch lens. These prints provide a sense of history without the clutter of more decorative Baroque styles.