i noticed something which nobody else did. in fuschia city, when we go to safari zone, we can access one part of it which we can't if we are in other place. there, we can encounter a missingno. it is twice your highest level poke and also is flying type which means that bolt strike and blizzard are the moves to be used. when we are battling it, if we click on restart battle, we get a message " important message-you can't restart wild battles"

see, you get what i am trying to ask? that must mean that there are more wild battles which can be fought. and that also mean that there are more secret passages...
if you didn't notice, there are 10 maps and 10 cities in kanto. then, that means all maps have a secret passage accessible only if you are in right town.
when you click on fushcia city on left hand side, you can see a map. you will see that there is the building used to access the secret path. then, to find the right city, we can see its map and find and try to enter that building in the map.
so far what secrets i know
fuschia city - safari zone
lavendar town - ghost town
please, if you know some secret paths, please share it.

oh...no answer

Complanbox Will You Like to Share that ghost town secret with me?
and there is more not in cities but you know rainbow/shadow mudkip you can even battle them and beat them to get rainbow/shadow key :)
But Others Secret I Dont Know :)
and that mudkip battles are disable for sometime by da man you can even catch them if you have special pokeballs which costs 3k coins something
<--- Credits To My Friend he told me that once :)