In 1539, Elector Joachim took Holy Communion – for the first time in line with Lutheran rites – at Spandau's St. Nikolai II church. In doing so, he officially introduced the Protestant Reformation to the Margraviate of Brandenburg. The Reformation History Museum of St. Nikolai is housed in a building across from the church, the core of which dates back to the Middle Ages. Inside, visitors can examine the old timbre frame. The museum's changing exhibitions deal mostly with church history and the history of the location and region. Among the items on display are paintings, sculptures, communion objects, liturgical books and documents drawn from the church's own collection.
One of the particular treasures of the museum, which is known as the Museum der Evangelischen Kirchengemeinde St. Nikolai Spandau, is the old church library consisting of roughly 3,000 historical volumes. The oldest manuscript dates back to 1447. The collection also includes incunabula, i.e. items printed before the year 1501 in Europe. The epochs most represented here are the Reformation and the Enlightenment. For example, a number of scientific and philosophical books are preserved from the 18th century, most of which originate from the library of the parish priest Georg Wilhelm Wegner (1692–1765).
Use of the library and archive is by appointment only.