  We propose a new model-independent mechanism for producing primordial black
holes from a period of multi-field inflation. This requires an enhancement of
primordial fluctuations at short scales compared to their value at CMB scales.
We show that such an amplification naturally occurs when the inflationary
trajectory exhibits a strong turn, that is a limited period during which the
trajectory strongly deviates from a geodesic in field space, and is sufficient
for subsequently producing primordial black holes with the abundance to be all
or a fraction of dark matter. Our mechanism is generic to models of inflation
realized in a multi-dimensional field space with an overlying potential and
geometry, also referred to as the inflationary landscape, as arises in
embeddings of inflation in high-energy theories. We study analytically and
numerically how the duration and the strength of the turn impact the primordial
fluctuation power spectrum and the abundance of primordial black holes. Our
mechanism has the potential of exhibiting unique features accessible to
observation through the primordial black hole spectrum and the stochastic
background of gravitational waves, offering a precious glimpse at the dynamics
of inflation.
