Grave monuments in the complex for Edebali (14th century). The one in the back seems to be the founder (of a dervisj-sect, is what I understood). Others are family members or followers.

Şeyh Edebali (1206-1325), also referred as Balışeyh, was the spiritual leader of Osman Gazi (the name giving Bey of the Ottoman dynasty) as well as his father-in-law. Before that, he had been a close friend of Ertuğrul Gazi, the father of Osman Gazi Bey.
This highly influential and respected Turkish Sufi Şeyh helped shape and develop the policies of the growing Ottoman State. His wise advice to his ruler (and son in law) is now preserved on marble:

“O my son! Now you are king! From now on, wrath is for us; for you, calm!
For us to be offended; for you to please! For us to accuse; for you to endure!
For us, helplessness and error; for you, tolerance! For us, quarrel; for you, justice!
For us, envy, rumor, slander; for you, forgiveness!
O my son!
From now on, it is for us to divide; for you to unite! For us, sloth; for you, warning and encouragement!
Be patient, a flower does not bloom before its time. Never forget: Let man flourish, and the state will also flourish!
Your burden is heavy, your task hard, your power hangs on a hair! May Allah be your helper! “.

On the picture: The cenotaph sarcophagi of Şeyh Edebali (the one covered in black) and of 12 of his male relatives.

Correspondent: J.M.Criel, Antwerpen.
Sources: ‘Türkye Tarihi Yerler Kılavuzu’ – M.Orhan Bayrak, Inkılâp Kitabevi, Istanbul, 1994 - Wikipedia,
& Personal visits (1997 – 1998).