Wide, deep, blind continuum surveys at submillimetre/millimetre (submm/mm) wavelengths are required to provide a full inventory of the dusty, distant Universe. However, conducting such necessary depth, with sub-arcsec angular resolution, is prohibitively time-consuming, even for most advanced submm/mm telescopes. Here, we report recent results from ALMACAL project, which exploits 'free' calibra...