The Windows walk is worth it. Nice gorge views and still loopable even though formally closed.

Windows Walk through old mine tunnels (light recommended) and over old railway tracks, a bit muddy. There are glowworms in the tunnels and windows for looking into the gorge. About an hour return, as the second half is closed. There's also a nice trail, about 1.5 hours along the river and through the 1km long illuminated tunnel.