Greek Prime Minister Alexis Tsipras yesterday visited the disputed landmarks of Hagia Sophia and a now-closed seminary in Turkey, in a sign of detente in the neighbouring countries' strained ties.
Istanbul's Hagia Sophia, a former church and mosque that is now a museum, often sparks tensions between Christians and Muslims over Islamic activities held there including the reading of verses from the Koran or collective prayers.
Its secular status allows believers of all faiths to meditate, reflect or simply enjoy its astonishing architecture of what is one of the most emblematic edifices of human civilisation.
But calls for it to serve again as a mosque have caused anger among Christians and raised tensions between historic foes and uneasy Nato allies Turkey and Greece.
Tspiras' symbolic visit to the Hagia Sophia came on the second day of his first trip to Turkey in four years.
The prime minister met Turkish presidential spokesman Ibrahim Kalin at the museum, an AFP correspondent said.
"You can feel the burden of history here," Tsipras told AFP.
The Greek premier listened enthusiastically as a guide accompanying the delegation explained the history of the edifice.
Police tightened security measures around the museum.
The Hagia Sophia was first built as a church in the sixth century under the Christian Byzantine Empire as the centrepiece of its capital Constantinople, today's Istanbul.
Almost immediately after the conquest of Constantinople by the Muslim Ottomans in 1453, it was converted into a mosque before becoming a secular museum in a key reform of the new post-Ottoman Turkish authorities under Mustafa Kemal Ataturk in the 1930s.
Ataturk was the founder of the Turkish republic.
Since Turkish President Recep Tayyip Erdogan's Justice and Development Party (AKP) came to power, critics and advocates of secularism fear the government harbours a hidden agenda to reconvert the Hagia Sophia into a mosque.