Head north from Goldenrod onto rte. 35, go through National Park (you will end up on rte. 36), head east until you see the weird tree. Battle it (it's a Sudowoodo), then head north onto rte. 37, and ecruteak city should just follow north from there.
The itemfinder is in erecutek city somewhere in a home someone has it.
In erecutek city there is a kimono girl theater inside defeat each kimono girl then talk to the guy near the rhydon to get the HM surf.
Back where the kimono girls were first in there dancing place in erecutek city
Somewhere in erecutek city there is a house with a guy inside near a map he will ask if you like treasure hunting say yes and you get the itemfinder.
ecruteak city
Blackthorn City is a location in the game Pokemon Gold. To get there, you have to go through the Ice Path.
Cianwood City
Blackthorne city is not in Pokemon Diamond but in Pokemon Heart Gold/Soul Silver
Cianwood city.
in olivine city
The Pokemon League isn't in a city. The Pokemon League is on a place of its own. It is above victory road, and is east of Blackthorn city.
Aliza town