Lego The Lord of the Rings: The Return of the King
The design features Minas Tirith, The Black Gate, Barad-dur, the Tower of Cirith Ungol (with hidden Shelob on the back), and Mount Doom.
A tiny play feature is built into Mount Doom that allows you to drop the Lego ring of power into the top and it will come back out on the back!
Instructions can be accessed here and on Rebrickable.com.
You can follow the fun on Instagram: @BenBuildsLego