This study presents the damage vulnerability of historical masonry monumental structures surveyed after the 1999 Kocaeli and Duzce earthquakes in Turkey. The region was hit by five large (M-s >= 7.0) earthquakes during the 20th century. Older mosques with arches and domes and their minarets (slender towers) were among the most affected structures. While some of the religious and historical structures had virtually no damage, many structures suffered substantial damage or collapsed. In the city of Bolu alone, for example, approximately 600-year-old Imaret, 500-year-old Kadi, 300-year-old Sarachane, and 200-year-old Yildirim Bayezid mosques suffered significant structural damage after the 1999 earthquakes. Another mosque in Duzce partially collapsed. This study presents general factors contributing to the deterioration of historical structures, and also provides a brief overview of issues associated with modeling and analysis of historical masonry structures.