As we showed earlier this week, some of the cast of Game of Thrones is already in Croatia. Currently filming is occurring in Kastel Gomilica, which stands in for Braavos. We’re got pictures of the sets going into Klis Fortress for Meereen. Now the production has added a third location, one they’ve never filmed in before.

Sets are now going up in the town of Šibenik, Croatia, in the Fortress of St. John. According to their local news paper, Sibenik.in, these pictures are construction for something being filmed in Season 5.

Exactly what? Well, we’re not sure. But that never stops one from speculation! More pictures, a few guesses, and a vague book spoiler or three, after the jump.

As you can see from this picture and the one above, there’s a big stone circle in the center of a high walled area. My first thought was “large scale ceremony” on par with Melisandre burning the Seven a couple of seasons back. But this can’t be the work of the Red God. With Thoros seemingly gone, Melisandre is the only one in Westeros currently practicing that style of religious magic, and she’s snow bound up at The Wall, which doesn’t film here.

Who else has religious type ceremonies? We know over in King’s Landing, the High Sparrow has been cast. Even though his take on the Seven is more homespun than the city is used to, they are still in the city, which this isn’t. Plus, I can’t think of anything that doesn’t occur in front of the Sept in the square.

It’s not Dorne. They’re filming that in Spain next month. (Can’t wait for those set pictures either. The Water Gardens are one of my favorite settings.)

This leaves me only one logical conclusion: more Meereen. This jives because as we see more of Meereen, we need new sets. Meereen films here in Croatia. Most importantly, there’s a couple of large crowd in attendance at an event scenes that take place in Dany’s upcoming story line, one of which has many of our major characters in the same place at the same time.

Maybe? We’ll have to wait and see who shows up for filming. The local paper says it starts September 15th, so we’ll keep our eyes peeled.