The Romanesque round chapel on Leonhard-Übler-Platz is historically significant. It is dedicated to John the Baptist and Catherine of Alexandria. The core building with a diameter of approx. 5.60 meters was probably built around the middle of the 12th century and was expanded in the 13th century (first half or only around 1260/70?) with a three-quarter round apse. A frieze with various ornaments runs along the outside. The original entrance was on the north side, today it is on the west. From 1264 the Altenfurt round chapel belonged to the Egidien monastery in Nuremberg. After the Reformation, the chapel was profaned and temporarily used as a stable or storage cellar. It had been owned by the von Scheurl family since 1816. The damage from the Second World War could already be repaired in 1947/48. Eberhardt von Scheurl had the burnt-down roof structure of the round chapel restored to its original Romanesque style during the war. In 1950, remains of figurative frescoes from the 13th century were uncovered in the dome. The Catholic parish of St. Sebald bought the chapel and the surrounding property in 1950. On May 11, 1952, the round chapel was consecrated again
Source: Wikipedia