there is not an under ground like in diamond Pearl and platium
But there is an underground path going from celrilum to verrilum.
P.S. The one from celedon to lavender town is Shut of now even though it wasn't in leaf-green and fire-red ( I'm not sure wheater it was open in gold, silver, and crystel)
to the left of the floor
Use the ship that lead you to one island to go back to vermilion city then from there you can use Fly to reach celadon city.
Celadon City while surfing, Pokemon Mansion Floors 1,2, 3, and 4.
Its a southwest from the celadon city Pokemon center you can't miss it its a red/blue building.
use a super rod in the ponds or you could get it at the game corner at celadon city
you have to use the underground path it is the only WA to get to celadon city
Celadon City
in celadon city
celadon city
The Market in Celadon City.
You have to get the tea from the old lady in celadon mansion. She is on the first floor, next to some pokemon.
You can buy fire stones at the celadon city dept store.
Fire Stones can be purchased at the Celadon City Dept Store on the Fourth Floor.
its rare in fire red but here is the location of this pokemon: Pokémon Mansion, Celadon City
to the left of the floor
Use the ship that lead you to one island to go back to vermilion city then from there you can use Fly to reach celadon city.
Celadon City is left (<-) of Saffron City. If that doesn't help, check your map (get from Daisy in Pallet Town) or check the Pokemon Center's map and just see for yourself.