Requirements: 
From level 12;
This offer is available till September 4, 15:00 UTC (11:00 EST).
The grand prize is the Amsterdam museum (2,100 coins, 2-3 pearls2-5 energy every 20 hours; requires 6x8 squares; can be placed in any location). 
Don’t forget this is a grand prize, so its drop chance is much lower than for other gifts.
Each chest can be opened with 9 Keys.
There are 3 ways to get Keys:
1. Complete the quest:
Please note that there is only 1 quest in 3 parts, after that the other 2 possibilities remain. After you complete these 3 parts the quest icon for keys on the left side of the screen will disappear.
No timers! You can get keys during the chest offer only.

Treasure Hunting I (4 keys, 100 coins)
Collect 12 Trowels (Subway Station, Upgraded Subway Station)
Collect 10 Clamps (Electronics plant - when producing Mouse, Keyboard, Web camera, Phone, Laptop, Monitor, Tablet, Motherboard)
Train 4 Builders

Treasure Hunting II (4 keys, 150 coins)
Collect 24 Maps of the stars (Stationery Shop, Upgraded Stationery Shop)
Collect 30 Bandages (German House, Upgraded German House)
Ask friends for 8 Cords

Treasure Hunting III (4 keys, 200 coins)
Collect 32 Runes (Family House)
Collect 10 Amethysts. You can get from 1 to 3 items each time. (Luxury Apartment)
Collect 14 Scrolls Do not drop every time (Mansion)

2. Collect profits from the following buildings:
  • Lighthouse (2-3 keys every 24 hours)
  • Barcelona Church (4-7 every 24 hours),
  • French winery (2-3 keys every 18 hours),
  • Versailles Gardens (3-4 every 20 hours)
  • Mount Rushmore (1-2 keys every 12 hours),
  • Statue of Christ the Redeemer (3-4 keys every 16 hours),
  • Downtown Abbey (4-5 keys every 24 hours),
  • Singapore Gardens (2-3 keys every 12 hours);
3. Use the sale offer and buy some keys with pearls and cash:

SPECIAL OFFER WITH AMSTERDAM MUSEUM CHEST EVENT


⏳ This special is available to get till September 4, 201815:00 UTC (11:00 EST).
⏳ Each offer lasts for 12 hours once received!

Statue of Christ the Redeemer: 2600 coins, 3-5 energy, 2-4 pearls every 16 hours
Barcelona Church: 12000 coins, 5-10 energy, 5-7 pearls every 24 hours
Downtown Abbey: 4500 coins, 3-6 energy, 3-6 pearls every 24 hours
Singapore Gardens: 1700 coins every 12 hours
Portuguese Castle: 3850 coins, 2 energy every 18 hours
Berlin Gates: 2570 coins, 1-3 energy every 18 hours
Swedish Church: 2500 coins, 5 energy every 14 hours