There is only one area in the Ithaca Skyway: Ithaca. There are a total of six locations in Ithaca where treasure chests spawn. However, there are usually only two per realm, one in the Temple of Athena and the second in one of the other 5 locations. You can see all six locations marked on the map below, with corresponding (by letter) descriptions and images further down the page. Have fun!
*Note* For more information about my treasure chest guides, as well as links to the guides for other skyways, please click the following link: Guide to Treasure Chest Locations Main Page.
A) When you leave the docks, go to the right and into the building (Temple of Athena.) The chest is against the back wall.
B) Go around the left side of the Temple of Athena and the chest is in an alcove behind the building.
E) Go up the stairs and the chest is behind the two vendor stalls. This chest can spawn either behind the first stall or between the two stalls. Thank you to Swordroll and Chrissy for this information!
I hope this guide helps your pirates get richer quicker! Good luck and thanks for reading! :)