here is a poem and i donot understand what is to be understood from the last para

does the memory of past glories

bring tears to your eyes?

does the thought of royal stories

draw from your bosom tender sighs?

oh, greive not for the throne and the crown,

you who have seen persia, greece and rome drown

in seas of oblivion,

you who have seen them rise again with renewed vigour.

march on, march on, march on,

rousing yourselves from this fatal stupor.

harken, there sounds the clarion call,

we must build a new tajmahal

out of this dust,

we must, we must, we must.

by nazrul islam

plz help me to understand the meaning of the underlined stanza of the poem.