We have this one: Vesper Cat Furniture, Walnut, V-High Base https://www.amazon.com/dp/B00SOTG05S/ref=cm_sw_r_cp_api_2Gg8BbSRZTMPF
It’s on the smaller size (4 feet) but works well for our younger and adult Siberian. The top is a bit small for our adult Siberian but he still seems to love it and sprawls out on it even though he’s big for it. It is a nice looking tree and looks good in our house.
I think most cat trees are hideous, but I saw this Vesper one in someone's post on r/amateurroomporn and got it. I like the wood look versus the gross carpet look. They have other styles and they're also sold on Chewy and other sites besides Amazon so shopping around would be recommended.
There's also other stuff you can do like mount ascending cat shelves on your wall for them to lounge and play or transform different arrangements of cube organizers to make them a cat jungle gym.