Main Church of Beatae Mariae Virginis (BMV) Wolfenbüttel

The main church Beatae Mariae Virginis zu Wolfenbüttel is the first major Protestant church in the world. The name of the church means: "The Blessed Virgin Mary" and for this first "grandiose" church building of Protestantism there were no models in history. Duke Heinrich Julius, pioneer of the Reformation in Wolfenbüttel, commissioned the construction of the church, and in 1608 the ducal master builder Paul Francke began construction. The requirements were complex: on the one hand, the building should be able to be used as a place of worship for sermons and the Lord's Supper, on the other hand it should represent the splendor and power of the princes and serve as a burial place for the princely family.

The church has elements of Gothic (windows), Renaissance and Baroque (gables). This stylistic diversity is characteristic of the post-Gothic period, in which the elements of Gothic were deliberately used to convey "ancient venerability".
The history of the main church BMV is closely linked to the development of Wolfenbüttel into a ducal residence. To the east of the castle there was previously a small chapel dedicated to the Virgin Mary, which was first mentioned in documents in 1301. Duke Henry the Younger converted it into a ducal burial place in 1533, and the first large Protestant church was built on this site around half a century later, retaining the name. The trigger was a request from the "preachers and church fathers" with which they approached the reigning Duke Henry Julius in January 1604. He was also keen to build a new burial place for the princely family at the same time.
Construction began in 1608 under the direction of the ducal master builder Paul Francke. In 1613, work had progressed so far that Duke Heinrich Julius, who had died unexpectedly in Prague, could be buried in the new princely crypt. Despite the Thirty Years' War, construction work was largely completed by 1624. The temporary roof on the tower was not replaced by the current baroque spire until 1751. The portals on the north and south sides are attributed to the sculptor Jacob Meyerheine.
St. Mary's Church was intended to be a church for preaching and communion to proclaim the Reformation faith to the congregation, but at the same time to fulfill the desire for princely representation. Paul Francke drew on the Gothic concept of the Low German hall churches. At the same time, St. Mary's Church also shows ideas of "humanistic architecture" from Italy and the Dutch Renaissance. The total work of art, combined in its own "manner", is thus an example of German Mannerism. However, the west portal, completed in 1645, was clearly created in the Baroque style.
Source: Wikipedia

Unfortunately, I haven't been inside yet, but from the outside it's a very impressive building