Forgotten City Stage 1 is the first level of the fourth world. There are a lot of bombs in this level.
Sweep up some bombs and run into the next room. Stand back and shoot the Blue Dust Herder, the Blue Octoballoon and the two Purple Octoballoons. Then the next door will open. Defeat the Yellow Chrono Blob. Get a record. While using the record, jump on the end of the seesaw with the green circle. When normal time resumes, stand on the other side of the seesaw. You will fly into the air. Sweep up some bombs, and kill the two Blue Spikers and the Purple Octoballoon. Shoot the target to open the door leading to the next room. Kill the Blue Spiker, Yellow Chrono Blob, and Purple Octoballoon. Press the button to make the bridge come down. Cross the bridge and use a Pause or Rewind to cross the two collapsing bridges. Kill the Red Keropper and shoot the target. A balloon will appear. Sweep the chain on the balloon and ride to the next area. Kill the Green Gatekeeper. After passing the Gatekeeper, kill the Water Spirit, Red Keropper, and Blue Dust Herder. Follow the trail of gold to the goal.
Red: In the pool of green water in the area with the last four enemies.
Silver: Near the end, it is on a branch. Be careful not to fall off!
Gold: In the pool of green water, sweep up a large piece of trash. It leads to a secret passage to the medal.
Blue: Climb down the ladder in the area with the target that makes the balloon appear. The medal is in this area.
S+ Rank: Follow the level normally, but buy the TS-2000 Flame beforehand to use on the Water Spirits.