The Models of Old Poznan are a compact introduction to the city's early history, using scale models, lighting, and narration to show Poznan from its medieval beginnings through the 18th century. The presentation is useful near the start of a visit, especially if you want the Old Town and Ostrów Tumski to make more sense before walking them.
Shows are offered in several languages, including English, and take about half an hour. It is a small attraction rather than a large museum, but the format makes a dense stretch of local history easy to follow.