The Zeynel Abidin Mosque Complex and Mor Yakup Church stand as remarkable symbols of religious harmony that has thrived for centuries in the town of Nusaybin, historically known as ancient Nisibis, near Mardin. Situated merely 100 meters apart, the Mor Yakup Church lies to the east of the Zeynel Abidin Mosque. Both landmarks are located approximately 250 meters from the Syrian border. Zeynel Abidin Mosque The Zeynel Abidin Mosque Complex is an important historical and religious site located in Nusaybin, within Mardin Province, Turkey. This extensive complex includes a mosque, minaret, and the tombs of Zeynel Abidin and his sister Sitti Zeynep, who is believed to be a 13th-generation descendant of the Prophet Muhammad. In addition, the complex features fountains, madrasah rooms, a cemetery, and a modern ablution area. Based on an inscription found on the tombs, the complex dates back to the 12th century. The Mosque Complex, built using rough-cut stone, follows an L-shaped architectural layout and includes both an open courtyard and a garden area. On the eastern side of the courtyard stands a minaret constructed in 1956. The mosque itself has a square prayer hall known as the "harim", accessible through a northern entrance. This space is covered by cross-vaulted ceilings supported by massive stone columns. The mihrab and minbar are modern additions. Over time, the building has undergone several renovations, including the integration of a women’s prayer area into the main hall. An inscription in the madrasa notes that the original "masjid" was later enlarged and transformed into a mosque. According to another epigraph, the madrasah was expanded in 1891 through structural additions. At the southwestern corner of the mosque lie the tombs of Zeynel Abidin and Sitti Zeynep. These are dome-shaped tomb chambers, covered in green cloth adorned with Quranic inscriptions. Epigraphs above each entrance state that the tombs were constructed in 1159, while a separate inscription on Sitti Zeynep’s shrine records a restoration effort in 1821. Flanking the mosque on its eastern and western sides are two large cemeteries, home to ornately carved gravestones with turban motifs, marking the burial sites of Tayyi Tibe sheikhs from the late Ottoman era. Mor Yakup Church The church is named after Mor Yakup, a highly revered Assyrian saint who was born and raised in Nisibis (modern-day Nusaybin). In the year 309, he was appointed as the Bishop of Nisibis during an Episcopal assembly held at the Virgin Mary Church in Diyarbakır. In 313, he initiated the construction of a cathedral in Nisibis, a city that functioned as a key political and trade center of the Byzantine Empire. In 325, Mor Yakup participated in the First Council of Nicaea, accompanied by his disciple Mor Afrem (St. Ephrem), a prominent ascetic, scholar, and hymn composer. Upon their return to Nusaybin from Nicaea (modern İznik, Turkey), they began reviving the Nisibis School. This institution offered instruction in theology, philosophy, logic, literature, geometry, astronomy, medicine, and law. Established on the remnants of a former pagan school, this effort played a vital role in spreading Christianity across Mesopotamia by educating a new generation of believers. The current main church structure, among the oldest religious sites in Upper Mesopotamia, consists of two main sections. The southern part is divided into two chambers supported by opposing buttresses. In the eastern section lies a 7-meter-square courtyard, bordered by northern and southern walls that each feature two doorways. A single apse is positioned on the eastern side. An archway on the west connects to the second chamber of the complex. What sets the eastern side apart is its elaborate wall decoration. A series of continuous friezes adorn the door arches, apse, and western arch, with an additional frieze specifically crafted for the niche inside the apse. The buttresses in the southern section are topped with Corinthian-style capitals, although their orientations face west. On the north and south walls of the western area, there are doorways whose upper sections are decorated with arched motifs. These arches feature delicate ornamentation, particularly noticeable on the eastern sides of the doorframes. A central buttress is situated near one of the western doors, contributing a sense of architectural modernity for its time. The decorative details are especially distinctive, showcasing some of the earliest and most refined examples of ornamental design that can be dated back to the 5th and 6th centuries in northern Mesopotamia, potentially originating around 400 AD. The western buttresses are believed to have been added at a later stage. Attention should also be drawn to the architectural features of the southern part of the building. A dome with an inscription, constructed in 1872, covers the eastern square chamber and stands as a significant example of the period’s design. Additionally, a western chamber of the complex was built around the same time. Beneath the eastern square room lies a crypt-like space formed by capsules that constitute a sarcophagus, believed to house the remains of Mor Yakup. In 2014, the Zeynel Abidin Mosque Complex and Mor Yakup (Saint Jacob) Church were officially included in the UNESCO Tentative World Heritage List.