Silbury Hill 180
Image by Nucleus
Silbury Hill

(sil)barry white

Dunno about twin. there was the Hatfield barrow nearby and Marlborough mound still stands.
There is Gop hill in Wales and Totnes mound in Devon, along with the mound that Berry Pomeroy castle stands on.
What you found then?

It's not found, but rather 'heard about', from an unknown written source - local history. And it's the mound in Brampton, Cumbria, which is classed as a Motte and is covered in trees so no one notices the hill - and it's surrounded by buildings ...

No decent photographs of it beyond the civic, from a distance, type. I could post the site here as a Sacred Hill ?