How serious of sports activities do you plan on using the space for? What you show looks like it is more for toys, not sport.

All kinds of issues. Ones that take giant expenditures to resolve. If you have an unlimited budget, you can afford the engineering of a large open space thst has to bear weight. And the big drainage system that it will require. And the sound remediation system that it will require. And HVAC circulation and filtration system. And hit to the home appraisal. Cash build situation required.

Otherwide, pour a pad for a basketball hoop outside, which is where the kids should play anyway.

@Mark Bischak, Architect : Not much of a sports person. I was planning on setting up a gym in my basement but I guess this space does not look very practical?

there's a reasonable amount of engineering to manage the walls that retain all that earth without the floor level horizontal bracing (joists). You'd have to have really wide footings to have that not collapse inward. I have a retaining wall holding back 11' or so of earth with nothing on the other side. The "foot" that sticks out is about 8' wide on the earthen side and 3' on the clear side. I would expect the same here.

Heating and cooling is less of an issues considering the earth maintains a fairly constant temperature.

Very specific need though - I would only make the investment if this was a large part of your life, or, conversely, relatively speaking, a small part of your budget...

Why would you need a 2 storey gym ? You do not even need a extra high ceiling I have a whole gym in my 8’ ceiling basement this other idea is beyond what you need for sure.

The money may be better spent elsewhere, like hiring a real local architect.

Basketball hoop with a glass slider directly behind it, what can go wrong?

Has to be an under bridge dweller. No one is this disconnected from reality.

@C Marlin : They are actually used in many basketball courts with no issues.

I'm no architect, but I'm not sure why this would be radically different than any two story foyer? I'm also not sure why there would be any more engineering to retain the earth than a standard basement? Not knowing the rest of the house, I'm sure this room could be repurposed in the future. It wouldn't be a deal breaker for me as a buyer depending on what the rest of the house is like. It seems unique and I am intrigued.

@James Bennett: Good points. I am not sure how much different of an engineering challenge this is from a 2 story foyer or grand-room. I am anyway thinking of not going with this design but here is the full floor plan if you are interested. It does look intriguing: floor plan

You know what they say: build the house for the life you live, not the one you wish you live. If you don't play basketball now, you are not suddenltpy going to become an enthusiast just because there's a court there.

I've seen a bunch of those in homes in my area. Bigger concern for me is how loud/echoed it can get. Most people installed interior windows, so they could talk to their kids while up in the Kitchen etc.

IMO they're cool, but a poor investment. I'd sooner plan an outdoor space, or do a cheaper detatched pole barn for this and use it as a flex space. Could always looks at off-site garage condos to do a gym in too