Like many churches in Friesland, St. Martin's Church was built on a terp, a heightened piece of land to protect whatever was on it from floods. Several churches had been standing on this spot before this one, although the terp had been at least two metres lower when the first church was built. The current church dates from the early 15th century and was named St. Martinus until the Reformation of 1580, when it was conficated for protestant use. Although it also served as a pilgrims church in memory of St. Boniface, who had been murdered nearby in the year 754.
Originally St. Martin was a one-aisled building in Gothic style. The northern side-aisle was added in the late-16th century and has round-topped windows. For the construction of this side-aisle stones were used of the abbey-church that was demolished in 1589 as a result of the Reformation, and that had been standing next to this church. The facade of the original aisle has a stepped gable, a 20th-century reconstruction of an old situation as known from old drawings. At the back, built directly against the choir, is a consistory with a facade dating from 1734.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.