Object models capture key properties of object-oriented architectures, and they can highlight relationships between types, occurrences of sharing, and object encapsulation. We present a dynamic analysis to extract object models from legacy code bases. Our analysis reconstructs each intermediate heap from a log of object allocations and field writes, applies a sequence of abstraction-based operations to each heap, and combines the results into a single object model that conservatively approximates all observed heaps from the program’s execution. The resulting object models reflect many interesting and useful architectural properties.