Def 7, it was the first OS used at work that turned invisible… It didn’t need constant defragging, optimizing or registry hacks like 98, 2000 or XP used to. It was a workhorse.
That said, I haven’t used 11 yet. My company just announced that this year all PCs will stay on 10 for the foreseeable future.
In southern Spain you can’t dig without hitting some stone age stuff. My town was a known stop for travellers before the Romans took over because of fresh water wells. Eventually a roman road was built about two millenia ago, and still ride on it with my bike for some routes.
No old buildings remain, this was a roadside village and stuff was made cheap and not meant to last, but there is a funeral arrangement from 600 BC that was unearthed and sent to the national museum. More info