It is on a mountain you will need waterfall.
You walk up and down route 14 and after a couple of minutes, you'll find sage.
Route 14 swarms
You can get mienshao on route 14
north of route 14
The seven sages are found in: N's Castle, Route 18, route 14, Chargestone cave, cold storage, dreamyard and Relic castle.
In: Cold Storage Relic Castle Route 14 Route 18 Chargestone Cave Dreamyard Black City (ONLY if you have Black)
You just have to find them. Sage 1 - Dreamyard, in a previously inaccessible area, Sage 2 - Relic Castle, Sage 3 - Chargestone Cave, third level, Sage 4 - Cold Storage, inside a container, Sage 5 - Route 17, on the westernmost island, Sage 6 - Route 14, you need 'Waterfall' to reach him, Ghetsis - Captured at the end of the main plot, but escaped and can't be found (until Pokemon Grey, perhaps).
swellow can be found on route 14 wich is west of undella town
In the abundant shrine north of route 14
Between Undella Town and Back City/White Forest
Sage Rood - Route 18 (You need Surf to get to him) Route 18 can be found West of Nuvema. Sage Gorm - Dreamyard (You will find there is a path now for you to get up to the stairs that was previous blocked, head down and follow the path to him) Sage Ryoku - Relic Castle (Remember the base where there was door you couldn't get to previously? That is now open, head through there and you wil find him and pick up Volcarona if you want to) Sage Zinzolin - Cold Storage (Exactly where you found him last time) Sage Bronius - Chargestone Cave basement. Sage Giallo - Route 14 (You will need Surf/Waterfall). You don't need to find Ghetsis.
Route 14, route 18, the dreamyard, relic castle, the cold storage, and the charge stone cave