Santi Marcellino e Pietro al Laterano is dedicated to Saints Marcellinus and Peter, 4th century Roman martyrs, whose relics were brought here in 1256. The first church on the site was built by Pope Siricius in the 4th century, close to the Via Labicana's catacombs of Marcellinus and Peter, with an adjoining hospice which became a centre for pilgrims.
This church was restored by Pope Gregory III in the 8th century. In the 9th century, the remains of Saints Marcellinus and Peter putatively were transferred from the catacombs here to a church in Seligenstadt, Germany. When the church was rebuilt in 1256 by Pope Alexander IV, the martyrs' relics were putatively returned.
At Present, under the high altar is an urn containing relics of Saint Marcia. On the left side is an altar dedicated to the Blessed Virgin, with a copy of Guido Reni's The Virgin in Glory with Angels, St Joseph and St Rita. Next to it is the Chapel of Reconciliation. An image of the dedicatees was placed on the first column on the left from the entrance during this restoration, with an inscription recording the restoration. The hospice and church were then given in 1276 to the Confraternity of those Commended to the Saviour.
The present church is the result of Pope Benedict XIV's 1751 reconstruction. The present cube-shaped exterior is divided by pilaster strips in a Neoclassical style, but with a late-Baroque elements, including a dome influenced by the architecture of Borromini. The façade was designed by Girolamo Theodoli and the main altarpiece by Gaetano Lapis depicts the dedicatees' martyrdom. After that restoration, the church was awarded until 1906 for the worship of the Discalced Carmelites.
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.