I think it would be very helpful to establish a list of the best Dungeons in the US, and Canada. My choices for the best Dungeons are Atlanta Dungeon The Den of Indomitus and Pandora's Box. I believe these Dungeons best exemplify the high standards submissives and fetishists are seeking in a commercial space. From Atlanta Dungeon's iconic Mistress Ultra Violet, to the legendary Mistress Porsche Lynn, and Pandora's box always hosting a cast of breathtaking Dommes. I have never been disappointed by these great house's of BDSM.

Quite a few places mentioned in this thread from last year.
http://domina.ms/~domroot/thebuzz/ubbthreads.php?ubb=showflat&Main=3525&Number=20338#Post20338

From what I've read since then I think I'd also add Mistress Victoria Rage of Seattle and Miss Grey of San Francisco . Their spaces look pretty impressive too.

https://victoriarage.com/dungeon/

https://mygreyheaven.com/territory/eac3sg5ygwlf6fhge8yq2wqqzd4pok

I think the original post was about houses with multiple Dommes. But since you expanded it to include dungeons run by individual Dommes, Irene Boss's Compound in Pittsburgh qualifies.

I've been in many of the top commercial dungeons in the U.S. and Europe (including all three in the original post) and Irene's space equals or exceeds them all.