Properties of the GMCs within the science demonstration field: distributions of masses M (top-left), maximal lengths (top-centre), aspect ratios (top-right), average mass surface densities Σ (bottom-left), velocity dispersions σ_v (bottom-centre), and virial parameters α_vir (bottom-right). The light-grey histograms show the distributions of properties for all clouds, excluding ten clouds with |v_lsr| < 10  km s^-1, as those have large distance uncertainties. The dark-grey histograms show the sub-sample of clouds that have an ATLASGAL match. The dashed vertical line on the average surface density plot shows our estimated completeness limit, ~70 M_⊙ pc^-2, corresponding to ~3 × 10²¹ cm^-2.