The Byzantine and Christian Museum was founded in 1914. From 1930 on it has been housed in the "Ilisia" mansion, which belonged to the Duchess of Placentia and was built in 1848 by the architect Stamatis Kleanthes. It was transformed into a museum by the architect Aristotle Zachos. Today an addition is being made and a large extension with basement and buildings in part above ground. The architectural design is by Manos Perrakis.
The Byzantine and Christian Museum, which is based in Athens, is one of Greece’s national museums. Its areas of competency are centred on – but not limited to – religious artefacts of the Early Christian, Byzantine, Medieval, post-Byzantine and later periods which it exhibits, but also acquires, receives, preserves, conserves, records, documents, researches, studies, publishes and raises awareness of.

The museum has over 25,000 artefacts in its possession. The artefacts date from between the 3rd and 20th century AD, and their provenance encompasses the entire Greek world, as well as regions in which Hellenism flourished. The size and range of the collections and value of the exhibits makes the Museum a veritable treasury of Byzantine and post-Byzantine art and culture.