OP is apparently looking for 1D structures:
On one hand, a 3+1D Kerr black hole has a 1D ring singularity.
On the other hand, an event horizon has always codimension 1 in spacetime. Subtracting 1 time-direction, we would speak of the event-horizon in 3+1D as an "area". In 2+1D that becomes a "length".