The beacons were great fireplaces permanently manned by men of Gondor, and were placed on top of seven peaks in the range of the White Mountains. From east to west they were the Amon Dîn, Eilenach, Nardol, Erelas, Min-Rimmon, Calenhad and Amon Anwar (or Halifirien).
This is the scene from Lord of the Rings: The Return of the King in which Pippin sneaks up to the beacon in Minas Tirith and sets it ablaze. I always thought that this was a cool scene, and it seemed like it would be fun to recreate in Lego. Thanks for viewing!