Drobeta bridge
The bridge built by Trajan across the Danube at Drobeta was dismantled by Hadrian to prevent easy access to the Empire for hostile intruders; its piles were left in place and seemed to Dio, who had seen them, to show that there was nothing that could not be accomplished by human ingenuity. Its designer, Apollodorus of Damascus (below, pp. 791 f.) who was responsible also for the Forum of Trajan, with its column and library, was an architect of genius who would have been perfectly at ease in the company of Leonardo or Brunelleschi. He was certainly aware of his own abilities; indeed, his contemptuous opinion of the architectural efforts of Hadrian, a gifted amateur, was believed to have led to his exile and execution by that jealous man when he became Emperor. (Boardman, 1986)