The phenomenon of aimless web navigation, often compared to falling "down the rabbit hole," brings to light significant aspects of the Internet's "long tail" concept. This research examines whether longer, non-goal-oriented web sessions genuinely lead users into the long tail of digital libraries, thereby exploring the discoverability of cultural heritage. The focus of this study is on Gallica, the French national library's online platform. This work aims to identify and characterize such sessions within Gallica, defining rabbit holes as long and diversified navigation sessions. The difficulty lies in identifying rabbit holes within server logs, which requires a mixed-methods approach involving interviews, qualitative studies, and simple statistical analyses. Despite Gallica's lack of hypertextual structure, we show that users do engage in rabbit hole-like behavior, navigating through keyword searches and filters. The study's findings align with user testimonies. A crucial conclusion is that rabbit holes in Gallica do not generally lead users to less-consulted content. This limitation is attributed to the search engine, which users must somewhat "hack" to navigate effectively. Enhancing Gallica's discoverability tools without compromising the existing user experience is essential for improving content accessibility.