This map explains why last night's Game of Thrones was so terrifying

Spoilers ahead!

Last night's Game of Thrones ended with an intense battle between a few Crows, the Wildlings, and the White Walkers with their army of the undead. It was an amazing scene in a somewhat shaky season, but what's really frightening about these events is how close they took place to the rest of civilization.

"The Wall is 300 miles long – one of the few things we have a true scale for in Game of Thrones," Jonathan Roberts wrote in his blog Fantastic Maps. "That places Castle Black around 120 miles from Eastwatch-By-The-Sea. Hardhome is around 300 miles (as the crow walks) from Castle Black, but only 150 miles from Eastwatch."

Here's the full map:

That's not far, even on foot. "Assuming the dead walk slower than the living (2 miles an hour rather than 3), but need no sleep – the army of the dead could reach Eastwatch in just over three days," he continues. "However I’m going to guess that’s not what the immediate future holds."

The map comes from The Lands of Ice and Fire (A Game of Thrones): Maps from King's Landing to Across the Narrow Sea, a book that contains 12 full-color maps of the lands from the books. Roberts illustrated the maps, so he knows what he's talking about. The full blog post has a bit more insight, and is worth reading.

It's unlikely we're three days away from the White Walkers reaching the Wall, but it's scary to look at the map and see just how close they are.

This isn't a "some day" threat, this is something that could be happening the day after tomorrow. Winter is coming, and it's bringing the undead.