Back in the early 70's we build a house that had a TV like that. Since there were no "flat screen" TV's then, in our den there was a hole and shelf in the wall that backed into the guest room closet. It was pretty cool because the TV was flush with the wall - something that no one had back in the day
We had all kinds of shit like that - had a great architech and builder
I still wonder if the new owners know that the odd wooden storage slats in the foyer closet are there to put dining room table leafs in ;)
Also had a laundry shoot that emptied into the den - which was paneled on the bottom 3 feet (I think that was required back then, lol). They had the laundry shoot basket so hidden in the paneling that all you could see was a little knob - and only then if you looked close