Why were all ships that landed in the port at alexandria searched?

When ships landed at the port of Alexandria, vessels were searched, not for contraband but for books and maps. These were confiscated, copied and then returned to their owners. The copies were added to the library.

These lines describe the loss of the identity of the city though the loss of the empire state buildings.

Explanation:

The world trade center ad the twin towers of the empire state building had been the center and the symbol of US commerce for a long time and were a reminder of its financial power.

They were attacked and torn down and thus the poem concerns with the twin towers.

The poem talks from the perspective of a bird in the sky or perhaps anything in the skyline that misses the grandeur of the two buildings talking about the loss of what was unthinkable to lose.