Library Observatory recognizes a unique opportunity the emergence of the DPLA represents: both to imagine new ways of interacting with cultural and scientific resources and to reflect on what collections of such materials mean, what stories they tell. An observatory, after all, is more than a collection of telescopes; it’s also the community of people who maintain those instruments, peer through them, and tell one another stories about the stars. Through a nested, interactive collections graph, the DPLA's offerings are visualized by relative size, format, and type of object. Users can discern at a glance the scope and makeup of the DPLA's growing repository, which includes the collections of the Biodiversity Heritage Library, ARTstor, and the Internet Archive’s Open Library. Find an item of interest, and a click takes the user to the original record at its home institution. But Library Observatory offers more than a novel search experience for the DPLA. It is also intended to help us understand how collections are put together, and how an initiative like the DPLA helps libraries, archives, and other institutions talk to one another, learn from one another, and make our common cultural heritage accessible and interoperable for all. The DPLA Library Observatory is a project of metaLAB at Harvard, a multi-disciplinary research collaborative in the arts and humanities headquartered in the Berkman Center for Internet and Society. The graphic search tool is the first in a series of instruments for analysis and discovery that we’re planning for the Library Observatory. The app first took shape at the DPLA AppFest hosted in November 2012 at the Chattanooga Public Library; its ongoing development is supported by a DPLA Sprint grant.