There is a large plane tree opposite the entrance to the Johanniter Castle, which provides shade for the whole square. Hippocrates, the forefather of modern medicine, is said to have planted the plane tree himself and taught it under this tree.
When the apostle Paul came to Kos a few centuries later, he taught Christianity under the same tree.
The floor around the plane tree is bordered by a low wall. There is an ancient sarcophagus on the north side of the wall. It was converted into a fountain during the Ottoman rule and served as a cleaning fountain for the neighboring loggia mosque.
The trunk diameter is over four meters and the crown diameter is about 18 m. The trunk has now been completely hollowed out due to insect and fungal attack. The rest of the trunk was painted on the inside with a protective red paint.
The branches have been supported with iron bars since 1975 so that they do not break due to their weight or the wind. In addition to the old trunk, two new shoots have grown from the roots of the tree, which means that the plane tree of Hippocrates will live on for many years to come.