"The lost city" of Petra (Jordan)

In a way Petra never really "died". There were always people living there and it was always a center of trade. It declined largely because there were alternative routes. Anyway hope this will help:

The sea route was partly responsible but the main reason was political hegemony. Rome was the first power to actually unify the entire region into one state for a long time. Before that there were several petty kingdoms under the nominal rule of this power or the influence of that power and they all had to pay tribute. With unification there was no need to pay tribute which was the main source of income to those desert cities that had no agricultural economy to talk about.