The church can be visited
St. Quintin Church

St. Quintin Church in Mainz is the parish church of the city's oldest documented parish.
History+
The first documented mention of St. Quintin Church occurred in 774, although its parish likely dates back to the Merovingian period, suggested by the patronage of Saint Quintin. It consistently served as a parish church and housed the first inner-city parish cemetery. Around 1300, the current Gothic structure was erected, consisting of a three-aisled hall nave. The bell tower in the southwestern bay served as a fire station until the 20th century and contained a tower keeper's residence from 1489. During the air raids on Mainz in World War II, the church was severely damaged in 1942, but its walls remained intact. Immediate reconstruction allowed for its reopening as early as 1948. The faithfully reconstructed spire was not reinstalled until 1995.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Quintinskirche_Mainz_2010.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 50.0009, 8.2721