From Entertainment Weekly:
The Game of Thrones prequel is officially underway.
Filming has quietly begun on the untitled follow-up to HBO’s fantasy sensation, which is shooting a pilot this summer in hopes for a series order. The shooting location is a familiar one: Northern Ireland, which served as the production of hub for GoT during its entire run. It’s not yet clear if the prequel will also shoot in other countries as well.
The GoT prequel is from showrunner Jane Goldman (X-Men: First Class) along with author George R.R. Martin and director S.J. Clarkson (Jessica Jones). The story is set thousands of years (roughly 5,000, according to Martin) before the events in GoT.
“Westeros is a very different place,” Martin told EW previously. “There’s no King’s Landing. There’s no Iron Throne. There are no Targaryens — Valyria has hardly begun to rise yet with its dragons and the great empire that it built. We’re dealing with a different and older world and hopefully that will be part of the fun of the series.”