Three Tree City is a rare Legendary Land card from Bloomburrow (BLB), collector number 260. Current market price: $28.89 (foil $34.44), TCGplayer market prices via Scryfall.
As Three Tree City enters, choose a creature type. {T}: Add {C}. {2}, {T}: Choose a color. Add an amount of mana of that color equal to the number of creatures you control of the chosen type.