Age of Empires III has made several innovations in the series, in particular with the addition of the "Home City", which combines real-time strategy and role-playing features.

Age of Empires III allows the player to play as eight different civilizations:[11] Spanish, British, French, Portuguese, Dutch, Russian, German, and Ottomans.

The native tribes featured are the Aztec, Carib, Cherokee, Comanche, Cree, Inca, Iroquois, Lakota, Maya, Nootka, Seminole, and Tupi.

[14] Three of these tribes were made playable in the expansion pack Age of Empires III: The WarChiefs: the Iroquois, Lakota (under the name Sioux) and Aztecs.

It cannot be attacked or destroyed, although an Imperial Age upgrade called "Blockade" stops the player's opponents from receiving Home City shipments.

The Home City is composed of five main buildings from which the player chooses their new shipment cards and customizations: The New World Trading Company, the Military Academy, the Cathedral, the Manufacturing Plant and the Harbor.

During the course of a game, players gain XP (experience) by completing actions such as constructing buildings, training units, killing enemies, and collecting treasures.

The units of Age of Empires III are based, as in previous iterations of the game, around military classes of the historic time period.

A new unit introduced in Age of Empires III is the explorer, which is chiefly responsible for scouting and gathering treasure but is also capable of building Trading Posts and has a special attack, used at the player's command.

Mercenaries are not trained like standard units; instead, they can be shipped from the Home City or hired from saloons for a lot of gold, so that only economically powerful players can employ them.

In most cases, a selection of Native American tribes populate game maps and support their own brand of military units that can be trained once an alliance has been formed.

In Florida, while Alain claims the lake, Morgan and Lizzie capture Spanish treasure ships and Sahin, killing Delgado in the process.

John and Kanyenke discover that the Circle plans to capture British and French colonies and towns while they are fighting, ultimately taking over North America.

Amelia, now wanting to avenge Cooper, learns from local Seminoles that an Inca city in Pacamayo Valley houses several barrels of the Fountain's water.

Back in the US, an elderly man congratulates Amelia and her destruction of the Circle, hinting that he is Morgan Black, who unwittingly drank from the Fountain of Youth and extended his life.

[27] This means that many events such as building destruction and tree falls will not be pre-created animations, but will be calculated according to the physics engine, in an innovation for the series.

Stephen Rippy, music and sound director at Ensemble Studios, said, "Age of Empires III is a game with an epic topic — it covers the colonization of the Americas over a period of some three hundred years, so it needed to have an epic-sounding score to match.

Using a full orchestra and choir as well as some more period-inspired instrumentation, the music follows the story of Morgan Black and his descendants as they battle the Circle of Ossus for a foothold in the New World."

The standard edition included the game and manual, a collector's edition version in a presentation box that includes the official soundtrack, extra documentation, a hardback book titled Art of Empires that contains concept art and 3D renders from the game and a DVD entitled The Making of Age of Empires III.

New content for existing European civilizations, maps and gameplay additions (such as the "revolution" feature, in which players can "revolt" from their mother country and start an active military coup in the game) was added.

Microsoft remedied this issue by assuring all customers who purchased the game that account keys would be generated within one week and automatically uploaded to each profile.

[40][41] The game features a campaign about the Great Siege of Malta that consists of 15 missions in which the player can control the Knights Hospitaller and must repel the invading Ottoman forces.

It also introduced new content in the form of two new playable civilizations, the Incas and Swedes, as well a new set of "Historical Battles" and "The Art of War" challenge missions similar to those implemented in Age of Empires II: Definitive Edition.

In a preview, IGN said that "After seeing the screenshots, our jaws hit the floor at the amount of detail",[69] while in their review, 1UP.com described it as "one of the most beautiful games you will put on your computer for the foreseeable future;"[53] GameSpy agreed, stating, "Age III's graphics are unmatched in the strategy genre.

[70] GameZone praised the game's sound effects, saying that "you will feel the explosions of the cannon balls, the muskets firing their endless volleys, and the destruction of a building.

Age of Empires III...avoids all the interesting and prickly issues like genocide, epidemics and slavery, instead subbing in a wimpy tale of a family destined to protect the Holy Grail from a Satanic Cult.

"[57] Age of Empires III's multiplayer was the first in the series to be integrated into the game interface and was highly lauded, as was the Home City concept.

The magazine's Brett Todd wrote: "It was astounding how Ensemble managed to stick to the historical RTS formula yet keep the gameplay feeling fresh.

Eurogamer shared these final thoughts and described the new Home City shipments, along with all the treasures scattered around the map, as silly and childish ways of trying to complement the game's lack of strategy and tactical choices.

However, Eurogamer recognized that Ensemble Studios was brave to implement "something quite different" from other real time strategy games — the Home City concept.