The katholikon of the monastery dates from a complete rebuilding in 1843. In plan it is the usual three-aisled basilica with a barrel-vaulted nave and flat ceilings over the side aisles, with the narthex on the west and the main semicircular apse protruding from the east end. The north aisle is named for the renowned icon displaced there—the Blessed Virgin of Consolation—surrounded by scenes from the Twelve Feasts of the Orthodox Church, an important Constantinopolitan work of the fourteenth century. The south aisle is dedicated to the Prophet Elijah, who is depicted in an icon along with fourteen scenes from his life, dated 1772. On the right side of the narthex there is a chapel dedicated to St. John the Evangelist and St. Germanos the Confessor, patriarch of Constantinople in the years 715-30.

The carved wooden iconostasis is richly decorated with floral, faunal, and heraldic motifs in perforated relief, as are the episcopal throne, the pulpit and the Oraia Pylai, or Beautiful Gates, in the center of the screen. Flanking the Oraia Pylai are icons of Christ Pantocrator, on the right, and the Virgin Hodigitria, on the left, the latter a work of the Cretan School dating from the sixteenth century. The icon of St. John the Baptist, with twelve scenes from his life, is probably also from the sixteenth century. Beneath it is the Hospitality of Abraham, which may date from the fifteenth century. Also on the iconostasis is a large icon depicting St. Photius, patron saint of the school, with an intricately worked silver covering done in Moscow in 1903. On the southern wall there is a large icon of the Virgin Hodigitria, possibly dating from the sixteenth century. Also noteworthy are the icon stands and candle stand in the narthex, all finely carved in wood with floral and heraldic motifs.

There are a number of tombs behind the church, including those of rectors and professors of the school as well as two patriarchs, Cyril VII (r. 1855-60) and Constantine V. (r. 1897-1901)

In Byzantine times, there were at least three monasteries on Heybeliada, then known as Halki. The most renowned of these was Hagia Triada, the Holy Trinity, whose site on Ümit Tepesi is occupied by the Greek Orthodox theological school of the same name, a direct descendant of the original Byzantine monastery. The present monastery is the most prominent monument on Heybeliada, dominating the view from an approaching ferry and from within the village itself.

The earliest reference to a monastery on Halki is in the writings of St. Theodore of Studius early in the ninth century. Theodore, abbot of Constantinople’s famous monastery of St. John of Studius, was exiled to a monastery on Halki by Leo V (r. 813-20) because of his criticism of the emperor’s iconoclastic policy. While on Halki, Theodore wrote a number of letters, theological treatises, and poems, one of which was addressed fondly to the monastic cell in which he was confined.

The monastery of the Holy Trinity was restored by the patriarch Photius I (r. 858-67, 877-86), who was twice exiled there, first between his two terms as patriarch and then in the years 887-90. Photius died in the monastery in 890 and was buried there; he was subsequently canonized and is today revered as the patron saint of the Theological School of the Holy Trinity.

The monastery was apparently destroyed at the time of the Turkish Conquest in 1453, moving one anonymous chronicler to lament the loss of what "had earlier been a place where wisdom and knowledge were studied, not only by monks but also by kings and noblemen." In 1550 the monastery was rebuilt or at least partially restored by the future patriarch Metrophanes III (r. 1565-72, 1579-80). Metrophanes also gave to the monastery some three hundred manuscripts, a priceless gift that formed the nucleus of what was to become one of the most renowned libraries in the Orthodox world after that of the Patriarchate in Istanbul.

Hagia Triada went through difficult times in the seventeenth and eighteenth centuries, but its finances, at least, improved after Peter the Great, Tsar of Russia (r. 1682-1725), issued a chrysobull giving the monastery a long-term endowment. The monastery was rebuilt and refurbished in 1773 through the efforts of its energetic abbot, Samuel the Deaf. The monastery was badly damaged in 1821, at the beginning of the Greek War of Independence, when it was attacked by a mob and set on fire. The monastery was rebuilt in 1844 by Patriarch Germanos IV, who decreed in a synod that "a theological school should be built for a purpose pleasing to God and dwelt in by theology teachers, priests who wish to learn, and future priests." Wooden buildings were erected to house the classrooms, study hall, teachers’ quarters, student dormitories, refectory, infirmary, and patriarchal apartments, while a two-storey stone structure was built for the library. Then in 1891 a three-storey wing was added to house the administrative offices and new dormitories. All of these structures were seriously damaged in the great earthquake of 1894. Thus a completely new building had to be erected for the monastery, all of the funds for which were provided by the philanthropist Pavlos Skylitsis Stephanovik. The new monastery was designed by the architect Pericles Photiades, and the building was officially dedicated on 6 October 1896, the archimandrite Germanos Gregoras presiding as Rector of the Theological School.

Theological School

The main entrance to the theological school is a combination of neo-classical and neo-Byzantine styles. Two monoliths of Proconnesian marble crowned with intricately carved Corinthian-type capitals divide the front of the porch, with smaller columns of the same type supporting the stilted arches of the tripartite window above. Four columns identical to those in the porch support the ornately painted ceiling of the entrance hall, from which a pair of marble stairways lead to the great reception hall on the main floor above. The walls of the reception hall are hung with portraits of patriarchs, rectors of the theological school, and others associated with the history of the monastery. At one end of the hall a niche contains the carved wooden iconostasis and its icons from the Byzantine church of the Virgin Kamariotissa on Heybeliada, which was taken over by the Turkish Navy in 1942. The patriarchal apartments, the administrative offices, and the rooms of the faculty are also on the main floor.

The classrooms of the school are situated on either side of the transverse corridor on the first floor, and the dormitories of the seminarians are in the north and south wings. The renowned library is also on the first floor as are the refectory, the infirmary, and service facilities such as the barber shop and tailor, while the gymnasium is to the south of the complex. The theological school was closed by the Turkish government in 1971, but political discussions are now under way which, hopefully, will lead to its reopening.

The mansion at #73 Refah Şehitleri Caddesi, originally known as the Mavromatakis Köşkü, is now open as a museum belonging to the Inönü Foundation, which is operated by the family of Ismet Inönü, first Turkish Prime Minister and later President of the Turkish Republic. Ismet Inönü, known as Ismet Paşa, first rented the house as a summer home in 1924, when he recuperated there after an illness. The Inönüs bought the house in 1934 for 9,500 liras, with new furniture presented to them as a gift by Atatürk. In September 1937, after leaving political office, Ismet Paşa settled into the house, where later that same year he was visited by the newly appointed Prime Minister Celal Bayar. During the years 1938-50, when he served as President of the Turkish Republic, Ismet Paşa stayed in the official summer residences at Florya and Yalova, because of the number of officials who made up his entourage, while his wife, Mevhibe Hanım, preferred to spend most of the summers in the house on Heybeli with their children, Ömer, Erdal, and Özden. During the years 1950-60, when Ismet Paşa was the leader of the opposition party, he spent most of the summers with his family on Heybeliada, where in his daily excursions to the beach he was accompanied by many of the townspeople, with the younger ones joining him as he jumped into the sea feet first from the pier. During his next term as Prime Minister, 1961-65, he still went to Heybeliada whenever his schedule allowed, and after leaving office he again spent his summers there. After his death in Ankara on 25 December 1973, at the age of eighty-nine, the house on Heybeli remained closed for a few years, but later Mevhibe Hanım occasionally returned along with her son Erdal and his wife, Sevinç, who had spent her summers in a neighboring house. Eventually the family decided to have the house preserved as a museum under the Inönü Foundation, restored just as it was when Ismet Paşa moved there in 1937, with the furniture presented to him by Atatürk. Here the visitor can see a variety of objects, pictures, and personal mementos of Ismet Paşa’s public and family life.

The large marble street-fountain on Turgut Yolu is the Heybeliada Çeşmesi, built in 1917.