The St. Vicelinkirche is the oldest and most historically significant church in Neumünster, dedicated to Bishop Vicelinus, the missionary who established the settlement in the 12th century. The church dates from that medieval foundation — though what you see today is a result of later modifications — and it survived the World War II bombing that destroyed much of the city centre relatively intact.
The interior is sober and Lutheran, as you would expect in northern Germany, but the building's age gives it a presence that the postwar streets around it lack. A short detour to look at the medieval stonework is worthwhile for anyone with an interest in Romanesque architecture or the history of Christianisation in northern Europe.