Tube Piano

An 88-key (standard piano) keyboard is 48œ inches from one end to the other. If you were to bend the two ends downward until they touched, making a circle, the diameter would be a bit shy of 15œ inches.

Aesthetically:
If you can imagine, take the frame and keyboard out of a grand, roll it up so one end touches the other with the keys on the outside, then sheath it in a wooden simplified conch shape, coated with 12 coats of black (or white, if you want to go there) high-gloss. Balanced on a pedestal like a telescope on its mount, the tube piano can (albeit with a bit of effort) be pointed in any reasonable direction. You can look through it. The pedals are still in front of the player, connected mechanically through the pedestal.

Technically:
The hammers would be mounted on the very inside, surrounded by the strings, those mounted on the harp (tension-bearing frame), attached to the tubular soundboard (note that in pianos the resonator is not under tension), that surrounded by the furniture. A bit of simple engineering with counterweighting, to balance the keys for a consistent touch throughout the octaves, and tadaa !

Ergonomically:
Better than a flat piano, with the proviso that hand crossovers are limited to the middle octaves unless you're double-jointed.

Musically:
There's quite a bit of wood on the conch shape for resonance and reflection: it should sound quite grandey.

subIdea: The Ring Keyboard (which was the original idea before I started typing)...
is generically useful for any single-manual keyboard instrument. A synthesizer controller would, from a distance, resemble a slightly large black and white striped tambourine, with a sloping disk inside to hold the electronic gizzardry. Modulation controls, which placement usually limits usage to the left-hand, would be inside the ring, available ambidexterously to the synth player.