Circle route

Not to be confused with Great-circle navigation, CircleRoute, or Spiral (railway).
"Circle route" could also refer to a number of railway lines named Circle Line.
High Street Kensington station on the Inner Circle line in London, the world's first circle line.

A circle route (also circumference, loop, ring route, ring line or orbital line) is a public transport route following a path approximating a circle or at least a closed curve.

Line 10 of the Beijing Subway, the world's second longest circular metro line