Pokémon Gold and Silver/Underground Path
From StrategyWiki, the video game walkthrough and strategy guide wiki
Go north out of the city, then turn right. There should be a house, so go inside it. Go down the stairs there is a Full Restore and an X Special down there. Pick it up and proceed through the tunnel.
It is a short cut to Route 6 to the South of Saffron, so it essentially lets you bypass the city.
