Once I stepped inside a racquetball court , and heard the acoustic of it , I said to myself I have to blow some harp in here... medium size room , hardwood floors and hard walls. It is not very easy to record in this kind of space especially when you use your phone for that , but it come out decent.
It was kind of funny , behind me where the glass door is , people were running on treadmills and working out on ellipticals...anyway , just another day at the gym.
Sounds great! I'd love to have a real room echo chamber for recording. That's how they did it on those early Chess records (over at Universal Recording, Chicago)
There is a space on the hill between my apartment building and the next one over. There is a berm running along the third side. Every time I walk that way I have to whistle just to hear the acoustics. :)