  Recent findings by the LHAASO experiment are opening a new window, that of
the PeV sky, to the observation of the electromagnetic spectrum. Several
astronomical objects emitting gamma-rays at energies well above 100 TeV have
been observed with the LHAASO-KM2 array of scintillators and muon detectors,
clearly demonstrating the feasibility of gamma-ray astronomy up to PeV
energies. An all-sky gamma-ray detector in the Southern Hemisphere, operating
in the GeV-PeV range, could complement LHAASO observations, monitor the Inner
Galaxy and the Galactic Center looking for PeVatrons. As shown by LHAASO, a
water-Cherenkov based detector is not well suited to measure the energy
spectrum up to the PeV range, nor to reach the advisable 100 GeV threshold. The
ARGO-YBJ experiment, operated for many years at 4300 m a.s.l. with an energy
threshold of about 300 GeV, demonstrated, on the contrary, the capability of a
carpet of Resistive Plate Chambers (RPCs) to fully reconstruct showers starting
from the GeV range up to about 10 PeV. In this contribution we propose a hybrid
detector made of a layer of RPCs on top of a water Cherenkov facility devoted
to the detection of muons for the selection of gamma-induced showers by the
muon-poor technique. We present the layout and discuss the expected
performance.
