If you are at the Ruined Highway Interchange and turn to face between the west and northwest of your compass, what unmarked location is that? I can't find a way to get to it.

You mean the Crow's Nest? There's a missile you have to detonate and a few marked men. After that you will run into a few deathclaws.

It's a broken building structure leaning across the High Road. There are a few arrows pointing the way and you have to climb up, over the rubble.