It represents Nora's anger about the inequality between men and women.
OR
Both seem to apply, she is frustrated that she has to depend all on her husband, how her life is in his hands, fitting into the explanation of the dance representing a women frustration in oppression. It also fits the Interpretation of the venomous spider because the crimes and the lies she has held secret might soon have a "venomous" effect in the household.
Several reasons actually. The most important one was its location. Thanks to it it enabeled the trade with African, European and Asian countries. Another thing is that it also was a good place to start a war on other countries.
