In the first quarter of the 9th century, when the pious Ludwig, son of
Charlemagne, was struggling with his misguided children for the
imperial crown, a church was built in Coblenz to St. Castor, the
missionary who had spread christianity in the valley of the Moselle.
The four-towered edifice arose on a branch of the Rhine.
The palace of the Frankish king stood at this time on the highest
south-western point of Coblenz, on the site of a former Roman fort,
and near by was a nunnery, dedicated to St. Castor. In this building
lived Riza, a daughter of Ludwig the Pious, who had early dedicated
her life to the church. Every day this king's daughter went to mass in
the Castor church on the opposite side of the Rhine. So great grace
had Riza found in the sight of Our Lord, that like His disciple of old
on the sea of Genesareth, she walked over the Rhine dry-footed to the
holy sacrament in St. Castor's. One day, the sacred legend goes on to
say, the stream was agitated by a storm. For the first time doubt
entered the maiden's heart as her foot touched the waves. Prudently
tearing a prop from a neighbouring vineyard, she took it with her for
a staff over the troubled waters. But after a few timid steps, she
sank like St. Peter on the Galilean lake. In this wretched plight she
became full of remorse for her want of faith in God. She flung the
stick far away, and lifting her arms towards heaven, committed herself
to the sole protection of the Almighty. At once she rose up from the
waves, and arrived, with dry feet as heretofore, on the other side.
More than ever after this did Riza, this saintly daughter of a saintly
king, strive to excel in those works which are pleasing to God. She
died within the cloister, and her bones were laid in the Castor
church, near the burial-place of the saint. Soon the popular
imagination canonised Riza, and her marble tomb is still to be seen in
the North transept of the Castor church at Coblenz.