Excuse my indulgence but there’s a good point to be made. It’s really fun to find places with lots of natural reverb to play harmonica. The key is lots of hard surfaces which the sound can bounce around in. Good places to try are stairwells, underpasses, empty garages, kitchens, bathrooms (it’s not the best hygiene but some public toilets are great), warehouses and so on.
What’s your favourite place to play harmonica? I’d love to know.