The collegiate church of San Cristoforo is the main place of Catholic worship in Barga, in the province of Lucca, home to the parish of the same name belonging to the pastoral unit of the same name of the archdiocese of Pisa.
On the external side walls of the Cathedral at the top and in the middle position there is a continuous motif with a series of arches, at the base of which a series of squares (tiles), sculpted with knots, geometric figures that express duality, human figures and dragons. The arches that ideally join two columns replaced by tiles signify the harmonious union of opposites, a theme so dear to the Templars.
  The church was built at different times, with the original construction dating back to before the year 1000. Subsequent expansions highlight architectural and decorative elements of evocative beauty ranging from Romanesque to Gothic. With the construction of the two side chapels and the choir, the construction of the church was completed.

  On the sides of the cathedral inside panels there are symbolic figures including Solomon's knots, one of which on the left side, serpentine with a head with two ears, almost as if to allude to the serpents of Human Wisdom, i.e. the Initiates. The tiles and the nodes can be dated to the first expansion of the Cathedral which took place in the 12th-13th century.
 
Source:  http://www.sapienzamisterica.it/il-duomo-di-barga-templare.html