The commune covers 17.9 km² and has a population of 1,087 since the last population census.
Surrounded by the communes of Avezan, Magnas and Castelnau-d'Arbieu, Saint-Clar is located 9 km northeast of Fleurance, the largest town in the area.
The river Arrats, the river Auroue and the stream of Saint-Jean are the main rivers that cross the commune of Saint-Clar, located at an altitude of 150 meters.
- The market hall
Its construction is attested since the 17th century. It is the successor of a medieval market probably located in the same place. The current market was strongly modified in the 19th century with the construction of the town hall in 1818 to which a campanile was added ten years later. They have all been reworked from the 19th century until the contemporary period.
- Saint Catherine's Church
Located in the heart of the "castet bielh", it forms the core of what was the first settlement of the village. The oldest part is the bell tower, which probably dates back to the 11th century. It was modified in modern times with the addition of the bell chamber at the top. The present nave of the church dates from the end of the 13th century. In the 14th century two chapels were added, one dedicated to Saint Catherine and the other to Saint Roch. On the south wall, a beautiful series of enfeus remains on the street side while remains of frescoes can still be seen inside the building. The nave of the church was amputated in 1854 to enlarge the square and the building was disused in 1862, when the new church was built. The "old church" was divided into lots and used as a barn, garage, house, cinema, etc. Today it has been restored to its former glory and is used for cultural purposes.
- Saint Clair Church
Built from 1857 to 1862 on the site of the old cemetery, it adopts the neo-gothic style that was fashionable at the time. It has a nice little organ recently restored.
- The "Plaçote" (or Republic Square)
It has two arcades, or corner posts. It was added to the village in the 14th century and was closed until the 19th century by a fortified gate.
- The roundabout way
On the East side, its route follows the old line of fortifications from the 14th century, the remains of which are still visible in the walls of the houses. It continues to the west, encircling the old bastide. The view of the Arrats valley to the east and the Gramont hillsides to the west is particularly remarkable.
It owes its name to Saint-Clair, the first bishop of Albi, an itinerant apostle martyred in Lectoure.
The bastide has two squares with arcades, or "cornices", a rare occurrence, not far from each other. In the center is the Place de l'Hotel de Ville with its "garland" of beautiful stone houses and its market hall with wooden pillars created in the 13th century and then reworked over the centuries until the 19th century.