Is there any Mega menu module? I am building a web site using drupal 8 and I want add a mega menu (3 columns menu with images) to the site.

Previously I have used TB Mega menu, but it does not support Drupal 8. Is there any mega menu module that supports Drupal 8, or is there a work-around which allows to install TB Mega menu on Drupal 8?
You can try the Ultimenu module. It has Drupal 8 version too and it's stable.

https://www.drupal.org/project/ultimenu


  Ultimenu is the UltimatelyDeadSimple™ megamenu ever with dynamic
  region creation.
  
  The module manages the toggle of Ultimenu blocks, regions, and a skins
  library, while leaving the management of block, menu and regions to
  Drupal.