piano scale
G♭ whole tone
G♭1A♭2B♭3C♯4D♯5E♯6
Six notes, every step a whole one. There are only two of these scales in all, and every note can be heard as the tonic.
The same sounds spelled from the other side are F♯ whole tone.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
G♭WA♭WB♭WCWDWEWG♭
What is true of it
G♭ whole tone is G♭, A♭, B♭, C, D and E, and back to G♭.
Its steps are W – W – W – W – W – W, where W is a whole step and H a half.
Chords made only of these notes
Found by testing every chord in the catalogue against these 6 sounds, not chosen.