According to Joystiq, the Robot Entertainment-developed Age of Empires Online will feature a number of social and MMO-like components, beginning with a capital city feature that sounds a little like the one available in Age of Empires 3.

In each capital city--one per faction--players will rule over their empire. The spot will act as a persistent home office for their attempt at world domination (or for finding quests) as well as an interaction point between players. Visitors can join you for a co-op missions or spend in-game currency at your world's shops. Rather than offer multiple pieces of premium content, Microsoft will give players the choice between the free version of the game and a single purchase premium upgrade.

For gamers who love recognition, Age of Empires Online will also offer Games for Windows Live achievements.

Free vs. Paid Content Cheat Sheet [from Microsoft, via Joystiq]

Key Features, Free to Play Familiar Age of Empires gameplay, downloadable from any PC for free*!

• The greatest ancient civilizations, including Greeks and Egyptians
• Constantly new, exciting and evolving content
• Quest, battle, chat and trade with other players - all free!
• Build and show off your own custom Capital City
• Enjoy historical settings with gorgeous visuals and a cool new art style

And that's just where the experience starts! When you're ready, you can unlock even more fun ways to play with premium content!

Additional Premium Content for Purchase
Take your civilizations to the next level by purchasing a Premium Civilization Pack, which adds a tremendous amount of gameplay and offers entirely new experiences. Premium civilization packs add the following to your gameplay experience:

• Rare and Epic Gear: Unlock Rare and Epic Gear! Not only will your units be more powerful with their upgraded gear, but many will have a unique design to make them stand out in battle. Advisors - In the Advisor Hall you can unlock Unique Units like Armored Elephants and Civilization Powers.
• Tech Tree: Experience the full tech tree with fantastic end game "Star Techs." For example, generate resources from your market, have your troops bandage themselves, or make your people immune to conversion in battle. Initiate Player vs. Player games - Set the gameplay parameters and invite your friends to play,
• Additional Inventory Slots: More than double your inventory space.
• More Workshops: Drastically improve your capital's production with more workshops to create all of the materials you need for crafting.
• Crafting Halls: Learn unit enhancements from additional Crafting Halls and use them to your advantage in the game. There are seven to choose from, including the Military College (enhances infantry), Hunting Lodge (enhances archers/missile units), and Cavalry Hall (enhances mounted units).
• Empire Points: Gives you the ability to spend Empire Points on the best loot in the game. Empire Points reward you for having multiple civilizations.
• In-Game Stores: The ability to earn in-game currency from the stores in your capital city.

And that is just the civilization! We will create a variety of ongoing new content that will continually offer you a fresh and custom experience.

*Broadband Internet required (sold separately).