Kaynarca is a Pinarhisar town, where 2334 people live according to 2012 Population Census. Kaynarca locates on old İstanbul Road and 5 km away from Pinarhisar Town. This area was being called as “Yene” (Water Source), when Persian King Darius came here in 513 B.C.
Byzantines Feudal Landlord of Kaynarca was holding the Kaynarca Castle, most of the people was living outside of the castle and were busy with farming and stockbreeding, when Kaynarca was conquered by I. Murat in 1369
Evliya Celebi, who came to Kaynarca in 1658, wrote that the castle, which was built on one-piece rock by Byzantines Emperor Konstantin , was pentagonal, small and ruined. Also Evliya Celebi inditaced that the castle was destroyed by command of I. Murat because of its hardly conquest. He also wrote that castle environment was well-kept and prosperous.
There is a registered Church Ruin, a Rock Monastery, a Hill Town, and 3 civil architecture samples in Kaynarca, which has a border with Pinarhisar Town, Bayramdere, Karincak, Cayirdere, Akoren and Erenler.