6.5 miles, 1800ft.

Park on the red circle below, and either load the GPX file into your GPS, or follow your nose!

You may have to scroll that map to the left to see the red circle. And the parking place is high up on the Black Road (Ffordd Ddu). Get there by turning off here, and following the road up. It's metalled at first, but soon gives way to being a dirt track with cattle grids. Go through the first gate that hasn't got a grid, and park on the left by the trees before you get to the second gate that hasn't got a grid. Walk through that gate, here, then turn immediately right, and follow the fence.

When you get to the top, keep following the fence until you can see the path up to Twll yr Ogof, here. From there, just follow the track (do be careful about the sheer drop on your left!) until you get to Tyrau Mawr (The Big Towers), where there's a cache.

We didn't get there; I was feeling really rough, it was blowing hard, and was VERY cold. I have been there before; it's a very fine walk with amazing views over the Mawddach estuary, and on to Snowdon and the Lleyn penisnular on a fine day.