  We present high-resolution observations of a quiescent solar prominence which
was consisted of a vertical and a horizontal foot encircled by an overlying
spine, and counter-streaming mass flows were ubiquitous in the prominence.
While the horizontal foot and the spine were connecting to the solar surface,
the vertical foot was suspended above the solar surface and supported by a
semicircular bubble structure. The bubble first collapsed and then reformed at
a similar height, finally, it started to oscillate for a long time. We find
that the collapsing and oscillation of the bubble boundary were tightly
associated with a flare-like feature located at the bottom of the bubble. Based
on the observational results, we propose that the prominence should be composed
of an overlying horizontal spine encircling a low-lying horizontal and a
vertical foot, in which the horizontal foot was consisted of shorter field
lines running partially along the spine and with the both ends connecting to
the solar surface, while the vertical foot was consisted of piling-up dips due
to the sagging of the spine fields and supported by a bipolar magnetic system
formed by parasitic polarities (i.e., the bubble). The upflows in the vertical
foot were possibly caused by the magnetic reconnection at the separator between
the bubble and the overlying dips, which intruded into the persistent downflow
field and formed the picture of counter-streaming mass flows. In addition, the
counter-streaming flows in the horizontal foot were possibly caused by the
imbalanced pressure at the both ends.
