Trolanport is the capital city of Zilargo, and also it's largest port. The entire city is built on a system of canals, similar to something like Venice, and the city serves as a major trade hub for all of Khorvaire. Goods come in via sea from all over, and the city also serves as a main departure point for travelers going to or from Aerenel, Sarlona or Xen'drik.
Trolanport is also the home of Zilargo's shipbuilding industry, and is where House Cannith builds their famous airships (with the help of gnomish elemental binding, of course.)
Like most of the settlements in Zilargo, Trolanport is built on Dhakaani foundations, though the ruins are in considerably better condition than they are elsewhere. Perhaps the gnomes took advantage of the strife caused by the kapaa'vola and moved in before the empire had even fallen.