Name:Greenhouse
ManaCost:2 G
Types:Enchantment Room
S:Mode$ Continuous | Affected$ Land.YouCtrl | AddAbility$ AnyMana | Description$ Lands you control have "{T}: Add one mana of any color."
SVar:AnyMana:AB$ Mana | Cost$ T | Produced$ Any | Amount$ 1 | SpellDescription$ Add one mana of any color.
AlternateMode:Split
Oracle:(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)\nLands you control have "{T}: Add one mana of any color."

ALTERNATE

Name:Rickety Gazebo
ManaCost:3 G
Types:Enchantment Room
T:Mode$ UnlockDoor | ValidPlayer$ You | ValidCard$ Card.Self | ThisDoor$ True | Execute$ TrigMill | TriggerDescription$ When you unlock this door, mill four cards, then return up to two permanent cards from among them to your hand.
SVar:TrigMill:DB$ Mill | NumCards$ 4 | Defined$ You | RememberMilled$ True | SubAbility$ DBChangeZone
SVar:DBChangeZone:DB$ ChangeZone | Hidden$ True | Origin$ Graveyard,Exile | Destination$ Hand | ChangeType$ Permanent.IsRemembered | ChangeNum$ 2 | SelectPrompt$ You may select a permanent card milled this way | SubAbility$ DBCleanup
SVar:DBCleanup:DB$ Cleanup | ClearRemembered$ True
Oracle:(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)\nWhen you unlock this door, mill four cards, then return up to two permanent cards from among them to your hand.