Excerpt from A Dance with Dragons ahead:
The old Valyrian road glimmered ahead of them like a long silver ribbon winding through wood and dale. For a little while Tyrion Lannister felt almost at peace. "Lomas Longstrider told it true. The road's a wonder."
"Lomas Longstrider?" asked Duck. "A scribe, long dead," said Haldon. "He spent his life traveling the world and writing about the lands he visited in two books he called Wonders and Wonders Made by Man."
"An uncle of mine gave them to me when I was just a boy," said Tyrion. "I read them until they fell to pieces."
"The gods made seven wonders, and mortal man made nine," quoted the Halfmaester.
A Dance with Dragons, Tyrion III
Tyrion and his companions mention seven wonders of nature and nine wonders crafted by men. The roads of Valyria are the fourth of the nine. Do we know what the other fifteen wonders are? I would assume The Wall to be another of the nine made by men.