Holy Trinity Greek Orthodox Church in located in the historic Greek neighborhood of Vienna's Innere Stadt. Greek Orthodox churches have existed near this site since 1787, as a result of the 1781 Patent of Toleration issued by Joseph II, Holy Roman Emperor. The architect of the 1787 building was Peter Mollner.
The current building is a Byzantine Revival re-design of the Mollner building by Danish-Austrian neo-classic architect Theophil Hansen. Greek-Austrian diplomat and philanthropist Simon Sinas funded the project, one of many collaborations with Hansen in Vienna and Athens. The cathedral was inaugurated on December 21, 1858.
The exterior features two-tone brickwork and gilded archways. The elaborately ornamented sanctuary shows a stylish allusion to Baroque church architecture typical of southern Germany and Austria. A number of frescoes for the facade and vestibule were commissioned from the Austrian painter and art professor Carl Rahl, with other frescoes by Ludwig Thiersch.
Since 1963 the cathedral has been the seat of the Greek Orthodox Metropolis of Austria.
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.