Wad where you step through a portal to choose your map?

I just played the 2016 dw project and the start reminded me of a mapset (dm I think) where you'd step through a window/portal to choose a map. It could have been one of the compilations of several megawads.

DUMP Series is one.

there's more, too.

DUMP, DUMP2, Couple of Duel map sets use it too :)
Golden Souls too

Sounds like the ZDL compilation or whatever it's called.

Reelism.pk3
Golden Souls.pk3

Memfis said:

Sounds like the ZDL compilation or whatever it's called.

Anyone got any idea what this is? Google is only bringing up the launcher of the same name.

The Duel32/40 WADs!