I'd call it a
"Fortress of Solitude for babies."
The Big Bang Theory Season 10, Episode 6
The greatest FORTRESS ever built.
Game of Thrones Season 2, Episode 7
Welcome to my FORTRESS of solitude.
The Big Bang Theory Season 8, Episode 7
...I will be enjoying a blissful evening
in my personal Fortress of Solitude.
The Big Bang Theory Season 2, Episode 21
We are about to enter Atzel's FORTRESS.
The Big Bang Theory Season 2, Episode 3