The ancient Greeks wrote several lists of ancient wonders. Each list had 7 selections because to the ancient Greeks 7 was a magical number. Many of the magnificent structures selected were located in ancient Greece, but not all of them.
The ancient Greeks loved lists. There was a time period in which some Greeks attempted to create a list of the most magnificent structures in the world they knew. They called these structures "wonders". Wonders were sights or things to be seen. The selection of 7 wonders acted somewhat like a suggested tourist guide, or sights not to miss.
Most of the lists various Greeks created agreed with 6 of 7 wonders. It would be very hard to overlook the Pyramid at Giza in Egypt, for example. The legend of the Hanging Gardens of Babylon in ancient Mesopotamia caught their romantic interest. Also found on most lists were the Statue of Zeus at Olympia, the Temple of Artemis, the Mausoleum at Halicarnassus, and the Colossus of Rhodes. But the Greeks were not in agreement with the selection of the 7th wonder. Actually, they never agreed. Philo's list is the one we use today. Philo was a Greek engineer and mathematician. He selected the Lighthouse at Alexandria as the 7th wonder.
Some of the wonders that did not make Philo's list included Babylon's Wall and the Ishtar Gate, both located in ancient Mesopotamia. Another popular choice not on his list was the palace in Persia. Many amazing structures were built in ancient times. Because the ancient Greeks had limited themselves to only 7 selections, various Greek writers had a difficult time agreeing on a list. Here's Philo's list: