The Seven Wonders were wonders because they were among the most popular tourist destinations; even as early as 1600 BC, tourist graffiti was scrawled on monuments in the Egyptian Valley of the Kings (by which time the Great Sphinx of Giza was already a thousand years old). It is notable that the Seven Wonders sites were all man-made; no natural features were included since they were not popular destinations.
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The commonly known Seven Ancient Wonders of the World were all man-made monuments, selected by Philon of Byzantium in 200 B.C. Today, only the Pyramids of Giza in Egypt remain.
His selection of wonders was essentially a travel guide for fellow Athenians, and the stunning sites were all located around the Mediterranean basin, the then-known world.