Game of Thrones filmed scenes at Italica ruins in Spain, rumored location for Dragonpit in season 7. According to Watchers on the Wall, at least 10 characters will be seen together for the first time in an epic scene.
Lena Headey (Cersei), Peter Dinklage (Tyrion), Emilia Clarke (Daenerys), Kit Harington (Jon Snow), Iain Glen (Jorah), Conleth Hill (Varys), Nathalie Emmanuel (Missandei), Anton Lesser (Qyburn), Rory McCann (Hound) and Hafthor Bjornsson (The Mountain) were present at the location. They have also confirmed that the scene involves a captured wight who is brought in as a proof of the White Walker threat.
** More Spoilers below **
The above information is in line with the ‘leaked’ season 7 plot which provides us with more information on the Dragonpit scene:
Meeting at the dragonpit with basically everyone. They demonstrate the reality of the white walkers and it terrifies Cersei (apparently the Mountain[or the Hound] chops up the wight and it keeps moving, Jon shows them the only way to kill it is with dragonglass or fire). She tells them she will send forces to help defeat the undead, but admits to Jamie she was lying. She wants the undead to clear out as many of her enemies as possible. Disgusted, Jamie begins to ride North. Likely happens episode 7. Tyrion takes a moment to talk to Cersei alone after the Dragonpit parlay.
If you wish to read the complete ‘leaked’ plot, click here.