GRE General Test: SE-932890 GRE Sentence Equivalence

The port city of Galveston, Texas, was once a great _____ of economic activity, but though great effort went into its reconstruction after the floods of 1900, it never returned to its former prosperity.
Select the two answer choices that, when used to complete the sentence, fit the meaning of the sentence as a whole and produce completed sentences that are alike in meaning