This strong tower is located on the place du Palais in Bordeaux, near the river Garonne. This was in the past an arc de triomphe raised in Charles VIII's honour, in 1493, on the foundations of a former gate put up in 1302. We could see a marble statue of the king Charles VIII in a central niche, put in there to celebrate his victory in Italy. This statue was destroyed during the French Revolution...
On the other side of the arc, there was a low-relief that represented cardinal André d'Espinay, archbishop of Bordeaux. The two towers of our gate was the former entrance of the palace called Ombrière, demolished in 1800; it was dukes of Aquitaine's residence then Parliament's seat.
But why did they called it Cailhau? Because the quay where our gate is located was nicknamed quai dal Caillau: Caillau, or caillou in French means "pebble". So, the quay was paved with pebbles from the river!