The fourth and final stage in SimCity Social's Sunken City event is perhaps the most challenging yet, requiring you to have expensive factories, complete a ton of jobs at the game's University, and have a massive amount of Sims living in your town. If you've made it this far though, it's doubtful that you're ready to stop, so here with a look at how to complete these quests in Act 4, thanks to the game's official forums.

H2OMG!

• Build the Hydrogen Cell Plant
• Produce 10,000 Materials at the Hydrogen Cell Plant

The Hydrogen Cell Plant is a Factory that can only be built after you've reached 80,000 Sims in population. Once you've hit that milestone, it costs 500,000 Simoleons to purchase, and takes building materials to complete. You'll need 12 Punchcards, six X-Rays, 10 Robot Workers, four Efficiency and one Kaizen to finish it off. Completing this first quest gives you 10 XP and six Artifact Shards.

Work It!

• Start 10 Attraction Jobs
• Start 10 Factory Jobs
• Start 10 Business Jobs

These three tasks are completed at the game's University, but thankfully, you can choose the shortest jobs available to complete these tasks more easily. Additionally, make sure to try the trick of starting a job and then storing the worker's home in order to cause the job to stop. This saves you time, while in theory still giving you the progress for this particular quest. When you complete the quest, you'll receive 10 XP and five Atlantean Cogs.

You-topia

• Collect from the Carbon Capture Inc. 5 Times
• Clear 15 Pollution Clouds

By the time you've reached this point, you're guaranteed to have a Carbon Capture Incorporated as it was required for a previous quest. That being the case, just make sure you collet from it as often as you can (every 21 hours), or feel free to pay Diamonds to speed up that timer. As for the Pollution Clouds, these form at random when tending Factories (of course, Factories with high pollution ratings would be more valuable here for once). You'll receive two Atlantean Seals and 12 XP for finishing this quest.

Pop Up City

• Have 150,000 Population
• Have 25 Level 9 Homes
• Collect from 100 Businesses

This is the big quest that will likely cause a lot of players to stall. Not only do you need 150,000 Sims living in your town, but you also need 25 Level 9 homes, which means that you've had to reorganize your town in such a way as to allow the massive decorations to pay out to tons of homes, with perhaps two decorations impacting the same set of homes. It's a process that's easier to understand in practice than in writing, but we wish you luck in pulling it off. You'll receive 12 XP and six more Artifact Shard for completing this quest.

Push for Profit

• Upgrade Carbon Capture Incorporated to 3-Stars
• Have a 3-Star Hydrogen Cell Plant
• Produce 25,000 Materials at the Hydrogen Cell Plant

These two building upgrades require dozens of different building materials to complete, ranging from Hard Hats and Cash Registers to Wrath, Vision and Big Ideas. You'll earn these by interacting with your friends' cities, completing University Jobs or simply asking your friends to send them to you outright, and if you can finish this quest with your sanity intact, you'll receive three Atlantean Seals and 15 XP.