Battlefield museum "Airborne Museum Hartenstein" is housed in a villa which served as the head-quarters of the Allied Forces during World War II. Since heavy fighting took place in the surrounding forest, many of its trees have bullets hidden inside them. We propose an augmented reality (AR) application which superimposes X-rays of the trees upon their trunk, revealing their hidden content. Our approach suggests that augmented reality, when deployed as a means to visualize what is inaccessible to human vision, can be relevant to cultural heritage applications. We present a working prototype of our application and conclude with reflection and future possibilities.