Hidden Grotto is a common Land card from Bloomburrow (BLB), collector number 254. Current market price: $0.28 (foil $0.33), TCGplayer market prices via Scryfall.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.) {T}: Add {C}. {1}, {T}: Add one mana of any color.