Dörtdivan
Dörtdivan is a district of Bolu. In 1990, when it was a town of Gerede district, it was transformed into a district. There are Byzantine castle ruins in Yağbaşlar Village in the district. On a hill between Yukarısayık and Sorkun villages, there are Himmet Dede Tomb, Kırklar Tomb in Kılıçlar village, Şehirban Dokuz Tomb in Çalköy, Secamehmet Dede Tomb next to Merkez Mosque. In addition, Ayvadibi Healing Water is located in the Mursel district of Yagbaslar Village. Köroğlu Festivals are held every year in July in Dörtdivan highlands. Çalköy, Çetikören, Aladağ, Karaçayır, Ömerpaşalar, Kapaklı and Kirazlı plateaus are the most important plateaus. Folk poet Köroğlu was born in Hesinler District of Aşağısayık Village, one of the district villages.
