You will need the HM strength(obviously) that you can get in the city with the lighthouse. You can get strength from the house underneath(not directly underneath but sorta to the left) the Poke center in that city, when you talk to the sailor sitting in front of the table.
Now you will need to go to cianwood city. When you enter the gym, talk to the boulder and use strength.(You will need a gym badge for using strength outside of battle!) Push the boulder on the left and on the right up and finally push the middle boulder to the left or right. then the path will be open.
Tip: After you beat the gym leader, walk out of the gym and talk to the lady just outside the gym. She will give you the HM02(Fly). :))
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The 5th Gym is in Cianwood City.
Someone gives one away in Cianwood City. To catch one of your own, use, Rock Smash on boulders in Cianwood City or Vermilion City.
Outside Cianwood City Gym.
He lives somewhere in goldenrod city he will be at his home after seeing him in the olivine city Pokemon center (or its cianwood city)
The 5th Gym is in Cianwood City in Pokemon Silver, Gold, and Crystal.