The GAMMA experiment is deployed on the South side of Mount Aragats in Armenia (Cosmic-ray observatory). The facility consists of a ground-based extensive air shower (EAS) array of 33 surface detection stations and 150 underground muon detectors. The elevation of the GAMMA facility is 3200 m above sea level, which corresponds to about 700 g/cm2 of atmospheric depth. The surface stations of the EAS array are arranged in 5 concentric circles of 20, 28, 50, 70, and 100 m radii, and each station contains 3 plastic scintillation detectors with the dimensions of 1 m × 1 m × 0.05 m. 9 central detector stations contain an additional small scintillator with dimensions 0.3 m × 0.3 m × 0.05 m for high particle density (much greater than 100 particles/m2) measurements. A photomultiplier tube is placed on the top of the aluminum casing covering each scintillator. One of three detectors of each station is viewed by two photomultipliers, one of which is designed for fast timing measurements. 150 underground muon detectors are compactly arranged in the underground hall under 2.3 kg/cm2 of concrete and rock providing the detection of shower muons with energy greater than 5 GeV.