Istanbul is one of the fast growing and historical cities in the world, and has many old cemeteries which have belonged to various empires. This study includes the first floristic and plant use results from one of these historical cemeteries (the Asiyan Cemetery). Vascular plants were collected from the cemetery in order to elaborate plant diversity. A total of 280 plant species was identified from an area of 29.1 decares. 139 of them are spontaneously wild growing taxa in the cemetery and the rest are cultivated on the graves. While the ratio of the area of the cemetery to the area of Istanbul is 0.1%, the cemetery includes 5.5% of the native plants of Istanbul. The steep sloped and stony parts of the cemetery have a native macchia vegetation consisting of Quercus coccifera L., Laurus nobilis L., Pistacia terebinthus L., Phillyrea latifolia L., Jasminum fruticans L., Rhamnus alaternus L., Ephedra foeminea Forssk., Osyris alba L. One of the most important results is the determination of the natural distribution of Rhamnus alaternus, Clematis flammula L. and Ephedra foeminea. This area is a refuge for these three species and the first native record area for R. alaternus in Istanbul. As a conclusion, in spite of covering a small area, the Asiyan Cemetery has a rich native and horticultural flora, and it is a refuge for three rare species, therefore the cemetery has an important role in urban plant diversity conservation.