In this mod, you can find a ton of new buildings, with their corresponding animated construction and destruction, ranging from the Barad-dûr tower itself to the plains and fields of the Rohan battle.
You will also come across 30 types of new units spread among 18 different factions. Elves, Orcs, Dwarfs, Hobbits, Uruk-Hai... they're all there, along with their corresponding animation, which must have been a project of titanic scale.
The best thing about it is that multiplayer still works. This means that if one of your friends has also installed the mod, you can challenge him to a battle on LAN.
Tales of Middle Earth is the most excellent mod for Age of Empires II of all time. When all is said and done, what are a few dozen more hours added to the hundreds you've already invested into the game?