  Using a differential magneto-optical technique to visualize flow of transport
currents, we reveal a new delocalization line within the reversible vortex
liquid region in the presence of a low density of columnar defects. This line
separates a homogeneous vortex liquid, in which all the vortices are
delocalized, from a heterogeneous "nanoliquid" phase, in which interconnected
nanodroplets of vortex liquid are caged in the pores of a solid skeleton formed
by vortices pinned on columnar defects. The nanoliquid phase displays high
correlation along the columnar defects but no transverse critical current.
