How do you get to Ecruteak city in gold?

Head up to Route 35 from Goldenrod City after getting the SquirtBottle from the Flower Shop. Go right and go up the two sets of stairs to the Odd "Tree". Use the SquirtBottle on it. Then head through the path behind the Odd "Tree". Once you get out of the trees, head North until you get to the gate. Go through. You will now be in Ecruteak City.