The Holy Trinity Church has a cross shaped plan with a dome. It is composed of the nave, narthex (entrance area) and the altar alcove. In the church many Byzantine architecture features have been skilfully used such as the inner organization of the space and the decorative and illuminative systems. These features, together with the pyramidal shape, forms and proportions give the church a picturesque appearance. The Byzantine architectural elements in the church have been combined with western architectural elements belonging to the same period.
Inside the church are two columns with reused capitals (thought to have been taken from classical ruins in the city). An inscription inside the church contains the name of Andronicus Paleologus (Governor of the province of Berat from 1302 to 1326), indicating that the church must have been built during the 13th or 14th century with his financial support.
References:The Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.