WebForms?

Yes, and classic ASP, WCF, ASP.NET 2.0, 3.5, 4.0, 4.5, etc…

It’s “fun” in the sense of piecing together history from subtle clues such as file owners, files on desktops of other admins’ profiles, etc…

I feel like this is what it must be like to open a pharaoh’s tomb. You get to step into someone else’s life from long ago, walk in their shoes for a bit, see the world through their eyes.

“What horrors did you witness brother sysadmin that made you abandon this place with uneaten takeaway lunch still on your desk next to the desiccated powder that once was a half drunk Red Bull?”