The public ESO near-IR variability survey (VVV) scanned the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey took 1929 hours of observations with the 4-metre VISTA telescope during five years (2010-2014), covering ~10^9 point sources across an area of 520 deg^2, including 33 known globular clusters and ~350 open clusters. The final product is a deep near-IR atlas in five passbands (0.9-2.5 microns) and a catalogue of more than 10^6 variable point sources. Unlike single-epoch surveys that, in most cases, only produce 2-D maps, the VVV variable star survey will enable the construction of a 3-D map of the surveyed region using well-understood distance indicators such as RR Lyrae stars, and Cepheids. The VISTA Variables in the Via Lactea (VVV) survey fourth data release (DR4) provides VISTA tile images and source lists in ZYJHKs filters, processed by the Cambridge Astronomical Survey Unit (CASU), for a total sky coverage of 560 square degrees. DR4 contains science data products from observations in the period 1 October 2013 - 15 October 2015, and also science data products from observations in September 2010 to September 2013 not included in the previous release. Original acknowledgement for data: Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 179.B-2002