Requirements: the chests given to players level 15+

The main reward is the San Francisco City Hall (4,300 coins, 1-3 energy, 1-3 candies every 24 hours, size 10*7, can be placed anywhere)

You can open each chest for 9 Autumn keys.
There are 3 ways to get Keys:

Completing the quest:

Pumpkin Soup, Apple Pie, and Stew I (3 keys)

Collect 13 Clothes Hangers (Textile Factory)
Collect 11 Carrots (Summer House, Upgraded Summer House)
Collect 8 Spiders (friends cities with coin or clock, do not drop every time)

Pumpkin Soup, Apple Pie, and Stew II (3 keys)

Collect 12 Bags of flour (Bistro, Upgraded Bistro)
Collect 11 Throw Blankets (Colonial House, Upgraded Colonial House)
Collect 6 Almond Butters (ask friends)

Pumpkin Soup, Apple Pie, and Stew III (4 keys)

Collect 11 Mint Leaves (Convenience Store, Upgraded Convenience Store)
Collect 13 Aqua Lungs (Shoe Shop, Upgraded Shoe Shop)
Collect 9 Pet Collars (Veterinary Clinic)

2. Collect profits from the following buildings:

Central Station 1 key (24 hours)
Museum of Paleontology 1 key (8 hours)
Ortakoy Mosque- 2-3 keys (24 hours)
Villa Augusta in Dordrecht 2-3 keys (24 hours)
Bruges Town Hall 2-3 keys (24 hours)

3. Use the sale offer!

Special offer with the San Francisco City Hall: Players level 17+

Villa Augustus in Dordrecht: 4000 coins, 1-4 energies, 1-4 candies, 2-3 Autumn Keys every 24 hours during the promotion. Size is 6*9 can be placed everywhere
Also available are the following buildings:

Bruges Town Hall: Every 24 hours: 4100 coins, 1-4 energies, 2-3 candies, 2-3 Autumn Keys during the promotion
Ortakoy Mosque: Every 24 hours: 4200 coins, 1-4 energies, 2-3 candies,2-3 Autumn Keys during the promotion
Bremen Town Hall: Every 24 hours: 3900 coins, 3-4 energies
Guildenband House: Every 23 hours: 4100 coins,1-4 energies
Tower LUMA Arles:  Every 24 hours: 4400 coins,1-3 energies