Journey to the Lost City is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

At the beginning of your upkeep, exile the top four cards of your library, then roll a d20. 1—9 | You may put a land card from among those cards onto the battlefield. 10—19 | Create a 2/2 green Wolf creature token, then put a +1/+1 counter on it for each creature card among those cards. 20 | Put all permanent cards exiled with this enchantment onto the battlefield, then sacrifice it.