My friends and I went to Castle Howard believing we could see the inside, but the day we visited it was closed. We still bought a ticket to go see the grounds, however, which was a sufficient second.
It was so grand and of such a magnitude, and very truly beautiful with its lakes, parks green lawns and fountains, and other buildings. This is a great attraction especially if you get to go inside, but also for a visit of the outside. You really get to see how the other half lived back in the day, and take in how much money it would take to live in and keep a place like this.
Very much fun! Would definitely recommend, and there should be no doubt especially if you get to see the inside.