Here HDRI map collected from the main Free resource online.
The HDRI (High-dynamic-range imaging) is used during the lighting and rendering 3D scenes process, simulating the lighting calculations in high dynamic range (HDR).

HDRI allows the preservation of details that may be lost due to limiting contrast ratios. Video games and computer-generated movies and VFX benefit from HDRi maps, creating more realistic scenes than with the more simplistic lighting models used.

Here the best free collection of HDRi maps to download: