Hansen was born in
Copenhagen. After training with Prussian architect
Karl Friedrich Schinkel and some years studying in Vienna, he moved to
Athens in 1837, where he studied architecture and design, with a concentration and interest in
Byzantine architecture. During his stay in Athens, Hansen designed his first building, the
National Observatory of Athens and two of the three contiguous buildings forming the so-called "Athenian Trilogy": the
Academy of Athens and the National Library of Greece, the third building of the trilogy being the
National and Capodistrian University of Athens, which was designed by his brother
Hans Christian Hansen (1803–1883). Along with Förster and many others, Hansen was one of the most important and influential architects of the Viennese
Ringstraße. His most famous work is the
Austrian Parliament building, which was created in the style of an ancient, neo-classic temple, and serves to refer to the Greek beginnings of
democracy. Hansen was originally a staunch critic of the Classical style that was taught to him at the Copenhagen Academy. Over the years, however, he came to incorporate Classical elements into his forms.
Bauleiter on this project was Swiss-Austrian architect
Hans Auer (1847–1906) who would go on to win the competition for the Swiss
Bundeshaus. , next to the
University of Athens and the
National Library (not shown) forming "the Athenian Trilogy". The academy and the university buildings were designed by Theophil Hansen (1885) in
Greek Ionic, academically correct even to the polychrome sculpture. The statues and columns were worked by
Leonidas Drosis. Hansen worked together with Austrian sculptor Vincenz Pilz (1816–1896) and artist
Carl Rahl (1812–1865), as well as with architect
Otto Wagner (1841–1918). In 1884 Emperor
Franz Joseph honoured Hansen with a
barony in the Austrian nobility and he was since styled "
Freiherr von Hansen".{{cite web|url= https://runeberg.org/nfca/0497.html |title =Pilz, Vincenz|website= Nordisk familjebok He died in 1891 in Vienna. ==Work==