It is a commune centre in the Târgu Secuiesc Depression, it lies at a 5 kms distance northward from Târgu Secuiesc, in the valley of the Casin. Administratively the commune consists of Sânzieni, Petriceni, Valea Seaca and Casinul Mic. Petriceni and Valea Seaca lie at the piedmont of the Turia Mountains, while Casinul Mic is situated at the piedmont of the Casinu-lui Secuiesc Mountains.
Due to its geographical location the commune is rich in archaeological finds. Here was excavated the Ariusd-styled painted ceramics from the Neolithic, the remains of the Bronze and Iron Ages and the heritage of the Goths. On the peak of Perko raising beyond Sanzieni a great reinforced settlement from the Bronze Age has been discovered, supposedly here stayed the questionable royal castle of Sanzieni as well. In the outskirts of Petriceni the place called by the people Polyvar turned out to be a Neolithic settlement. Several statuettes made of clay depicting animals have been excavated from here. In Valea Seaca a miniature Osiris-statuette has been discovered. In Petriceni and in Valea Seaca we can see the places of the old churches.
The first written mention of the commune centre dates back to 1251 (Zent Leiewkh), Valea Seaca was first mentioned in 1311 (Zarazpatak), Petriceni in 1332 (Pusulnic), Casinul Mic in 1567 (Kyskazon). The western part of Sfnzieni, Petriceni and Valea Seaca were settlements lived by pecenegis. They belonged to the latifundium of the Apor family from Turia and thus they were parts of the Felso-Feher county until 1876. The old name of Petriceni was Peselnek, it has been appearing as Petriceni only since 1906. It is mentioned that in 1241 the Tartars invading through the Oituz-pass ravaged the neighbouring villages and they carried off the inhabitants. During the Kuruc war of independence the Austrian army robbed and looted the people. In 1718 the population was thinned by plague. The war of independence in 1848-49 had fourteen victims. STnzieni is a religious place since the St. Istvan chapel on the peak of Perko Mountain has been a shrine for ages. As a result of the continuous development the population of the commune was slowly increasing. According to the census from 2002 the total population counts 4682 inhabitants out of which Sanzieni has 2780 residents, in Petriceni live 984
people, in Valea Seaca 628 and Casinul Mic has 290 inhabitants. The ethnical structure is as follows: 0,58% are Romanians, 99,27% Hungarians and 0,12% of other nationalities.
Sanzieni has always been an important settlement since it was crossed by a road which led to Casin and Ciuc across the Casin brook and directed towards the Oituz-pass through the northern villages of the ,,Holy Land". The main living in the commune is based on potato-growing, several families practice stone-cutting even today, the women cultivate weaving industry at home. After the change of regime the private capital has grown, agricultural farms came into being; today the commune has a mill and a bakery as well. Significant agricultural branches are the livestock-breeding and the silviculture. The commune centre has a railway station on the Sfantu Ghe-orghe-Bretcu secondary line. It has a mixed choir, a folk dance ensemble and a group which cultivates the old traditions and folk customs. Nevertheless it does not excel in tourism although it is rich in places of interst and valuable touristic objects, besides its subsoil has unexploit-ed acid-water. Its main sights are the Roman Catholic church (medieval monument), the St. Istvan chapel with four cusps situated on Perkfj Mountain in Sanzieni. It keeps remains of frescos (St. Istvan, St. Laszlo, St. Imre prince and St. Gellert bishop). Also in Sanzieni we can find the ruins of the Tarnoczy-Mikes-castle which appears in Kemeny Zsigmond's novel, Ozvegy es leanya (The Widow and Her Daughter). In Casinul Mic we can visit the memorial house of the pilgrims. In Petriceni a living custom is the wandering of the holy family, it is practiced by young people during Advent, they are looking for accommodation for the little Jesus. The son of Valea Seaca is Opra Benedek (1907-1978) illustrious teacher, he was vilified and imprisoned during the Hungarian war of independence in 1956, today he is the post humus laureate of the revolution. His name is beard by the local school.