The Ordekli Bath is an important fourteenth-century monument in Bursa, Turkey. The bath partially collapsed during the 1855 earthquakes. The plan, construction techniques and material properties of the bath have been investigated to determine whether they could have been partly responsible for the collapse of the men's frigidarium. In this study, the physical, mechanical and chemical properties of the original materials, sampled from both the stable and unstable parts of the bath, were examined and compared with each other The test results showed that the building materials used for the bath are incredibly durable. It is therefore proposed that the collapse of the men's frigidarium was not caused by the intrinsic properties of the materials from which the bath tons constructed. The collapse is thought to result from flaws in the original design and construction techniques used for the men's frigidarium.