The Benakis family belonged to the diaspora, the Greek communities scattered around the eastern Mediterranean during the long centuries when Greece itself was Ottoman territory. Emmanuel Benakis - Antonis' father - had built a cotton fortune in Alexandria, served as a Greek member of the Egyptian parliament, and eventually returned to Greece to serve as mayor of Athens. The family's emotional centre, though, stayed in Egypt. Antonis grew up among Coptic Christians, Sephardic Jews, Muslim Arabs, Italian merchants, and the trilingual Greek mercantile class. He went to Cambridge, married a young woman from the Egyptian Greek community, and started collecting in his thirties because the markets of Cairo and Alexandria were full of objects from a Greek past that nobody else seemed to want. By the time he turned forty-five he had assembled the largest private collection of Byzantine and Islamic art in the eastern Mediterranean.

The mansion was four storeys of Athenian neoclassical, on Vassilissis Sofias - the avenue that runs east from Syntagma Square along the National Garden, lined with embassies and the Presidential Palace. The collection that arrived with the building included more than 37,000 Islamic and Byzantine pieces alone. Benakis dedicated the museum to the memory of his father Emmanuel and stipulated that it remain free to enter on the days when ordinary working Athenians were most likely to visit. The Greek state, in 1930, was very poor and the museum was a remarkable gift; later acquisitions through the 1970s added 9,000 more objects, and the institution began to attract donations from other Greek collectors who liked the precedent. By the time Angelos Delivorrias took over the directorship in 1973, the museum had grown by another 60,000 items and the building could no longer hold them.

Delivorrias had a vision in 1973 that took until 2000 to realise. The flagship building, he argued, should focus exclusively on Greek culture from prehistory to the present - the unbroken thread of Hellenic civilization across seven thousand years. The Islamic art collection, the Chinese porcelain, the toy collection, the photo archive should be housed in their own dedicated buildings. An earthquake damaged the main building in the late 1990s, which paradoxically created the opportunity. A 20 million dollar restoration brought the mansion back, and in the year 2000 the renovated museum reopened with the Greek collection rearranged across three floors as a continuous chronological narrative: Cycladic figurines, archaic kouroi, classical pottery, Byzantine icons, Ottoman-era folk costumes, the war of independence, modern painting. The new arrangement had the strange effect of showing that Greek visual culture had not paused for two millennia of foreign rule but had quietly continued in icons, embroidery, and woodcarving.

The Islamic collection - about 8,000 pieces from the seventh through the nineteenth centuries - moved into a complex of renovated neoclassical houses in the Kerameikos district near the ancient Agora and the Theseion. Lambros Eftaxias, who had been honorary president of the museum's trustees, donated the buildings. The Benaki Museum of Islamic Art opened on 27 July 2004, three weeks before the Athens Olympics. Its collection ranks among the most important worldwide for the period and includes masterworks from India, Persia, Mesopotamia, Arabia, Egypt, North Africa, Sicily, Spain, and Asia Minor. The strongest holdings cover Ottoman art from the empire's sixteenth-century peak. Standing on the rooftop terrace, you can see the Theseion - the best-preserved Doric temple in the Greek world, fifth century BC - across the agora, with the Acropolis behind it. Forty-five centuries of architecture in a single rooftop view.

There is a strain of Greek collecting that begins not in Athens but in Alexandria, Smyrna, Constantinople, Trieste - the cities of the diaspora where Greek merchant families became wealthy enough to buy back what their ancestors' homeland had lost. The Benaki collection is the largest survivor of that strain. The Goulandris collection, which became the Museum of Cycladic Art, came from a similar source. The Levendis collection, the Phix collection, the Argyropoulos collection - all came from families who had grown rich abroad and returned with the conviction that Greek culture deserved a museum worthy of it. The Benaki Museum holds over 100,000 artifacts now, across multiple locations. It is one of Greece's foremost cultural institutions. It was made possible because a man who grew up in Egypt could not stop buying what nobody in Greece itself could afford to keep.