  We derive universal properties of the near-horizon geometry of spherically
symmetric black holes that follow from the observability of a regular apparent
horizon. Only two types of solutions are admissible. After reviewing their
properties we show that only a special form of the solutions of the second type
is consistent. We describe how these results extend to modified theories of
gravity, including Einstein--Cartan theories. Then we describe the unique black
hole formation scenario that necessarily involves both types of solutions. The
generalized surface gravity is infinite at the apparent horizon. This feature
and comparison of the required energy and timescales with the known
semiclassical results suggest that the observed astrophysical black holes are
horizonless ultra-compact objects, and the presence of a horizon is associated
with currently unknown physics.
