The most secure prison is one you build yourself.
Dr. Bruce Banner was one of the smartest people on the planet. He could hold converstations with Reed Richards and hold his own, a very rare feat. He was the leading expert in the effects of radiation, on biology, and in the top dozen for weapon technology.
At least, when he was Dr. Bruce Banner.
He only had one... small... problem. When he got horny, he transformed into a dumb, hulking beast with nothing but sex on his mind. And the hornier Hulk got, the bigger Hulk got.
On a world where nine out of ten of the population are sexually attractive females, he was horny nearly all the time. It made it difficult to retain his mind and do something other than fuck the entire day away.
Bruce had tried isolating himself, and it worked for a time, but then he would wake up with morning wood and three days would pass and the shack in the woods was destroyed.
And so, in another isolation moment, he wrote up detailed plans for a prison for the Hulk, to keep him contained and happy and not destroying cities with his lusts, and sent them to the person who wanted him contained more than anything. General "Thunderbolt"
Ross was only too happy to build the prison.
The furnishings in the main room were nigh indestructible. Cushions had to be replaced daily while the walking libido slept. Every decoration was designed to have a calming effect. If Banner wasn't there when he transformed, the Hulk knew he could go there
safely, and usually did.
The most important part was that thirty of the highest paid pleasure girls were on hand at all times, as well as a highly paid medical staff ready to deal with emergencies. Broken limbs were common, though despite the high libido and strength of the creature,
he was remarkably gentle for his size. He didn't want to hurt people, he just wanted to fuck them.
And when he was being particularly rough, they had his cousin on call.