The village of Laon sits about 80 miles northeast of Paris, and is the location of a well-preserved chapel built by the Knights Templar. The local museum has a collection of Roman and medieval jewelry, and the chapel itself sits within the museum's gardens. The chapel was built around 1180, serving the local commandery. Following the dissolution of the Order, the property was transferred to the Knights of St John (the Hospitallers).
While there are several round or octagonal churches in France, only three of them were actually built by the Templars. Laon's octagonal design was used as a model for a similar Templar chapel in Metz. The third was in Paris (Villeneuve du Temple).
From The Knights Templar Chapel and Tombs in Laon by Francois Hagnere:
[I]n 1128, Bishop Barthélémy de Vir attended the Council of Troyes where, upon approval of Pope Honorius II, Bernard de Clairvaux participated in the elaboration and writing of the Knights Templar Rule. As soon as he came back, the prelate welcomed the Knights Templar and offered them a house on the Rue sainte-Geneviève that would soon become Rue des Templiers. His liberalities towards the knights bearing the white cape and the red cross pattée did not stop here and donations followed at Puiseux where only an underground gallery remains today, at Thouny where a ruined chapel still exists and at Cerny-en-Laonnois and Bertaignemont where not even a stone of the old Templar houses still stands.
As from 1134, by derogation of Pope Honorius II, the Order was entitled to erect a chapel on their own cemetary in Laon. This is the chapel we visit today. The octagonal rotunda is shouldered by buttresses, the windows still belong to the Romanesque Style and the basis of the roofing presents a denticulated carved decoration with modillions that recalls the Mozarabic Style. The choir is quite simple with the same décor and the apse has a half dome. The bell tower is at the junction of the octagon with porch. This square porch has an ogival vault and later received a floor with a tribune towards the inside of the chapel. This octagon with a cupola confirms Viollet-le-Duc’s theory on Templar architecture, like in Metz, and also this sanctuary seems to have been created after the same plan as the chapel of Sainte-Madeleine (destroyed in 1690) in the nearby Benedictine Abbey of Saint-Vincent. At this time in Laon, the monks alone were allowed to possess cemetaries with a chapel and this architectural arrangement might have inspired the Knights Templar. The chapel housed the sepultures of the most illustrious of them.
Three tombs are still visible. Two of them belonged to Hospitallers of the Order of Saint-John of Jerusalem. The most recent one (XVIth century) shows an erased inscribing, the other one is that of Jacques de Haute-Vesnes who died in 1335. The Knight Templar tomb is the one of chaplain Grégoire, dead on the day of Saint-Martin, in 1268.