Šibenik, Croatia, is one of the new cities added to the impressively long list of Game of Thrones locations this year, and crews have arrived in town to prepare for filming.
According to Sibenik.in and several new photos (posted below), sets are under construction at the Fortress of St. John, readying the area for shooting September 15th through the 21st. The site reports that a dress rehearsal will take place in Šibenik on September 8th.
Built in 1646, the star-shaped fortress is located high above the old town center. Currently sets are being built on the inner portion of the fort. The purpose of the set is unknown, though it resembles a courtyard in progress or a minor fighting pit, from the looks of the photos below.