Note: Most Hidden stuff becomes available to the game once you gain access to the Warptowers' teleportation services.

The following Towns/Cities provides 3 side-quests each:

- Santa Cecilia Village
- Saymal Village
- Alpatina City
- Utania Village
- Respene Village

(Just approach the Mayor's office in each of these towns/cities.)

Hidden freebies/side-quests (After the signing of treaty):

- Mt. Guerro
- Thea's Orphanage
- Senna Woods (At the place where you fought the first boss)
- Senna Woods (Home)
- Santa Cecilia Village (Grandma Mely's house)

Summons:

- Mt. Glacius (Acquire Crema)
- Zermo's Lair (Acquire Zermo)
- Quas Ruins (Acquire Excar)
- Senna Woods (Acquire Divina and Lianna)

Note: Summons are attainable once you've received your first set of Arc stones for the free-roaming stage of the game.

Hidden Party member:

- You'll receive a "Special Key" from River at the later parts of the game. Use this key to open the locked house at Xmeil village, the one with crystals adorned around it. Inside, you'll find the Hidden Party member as well as a chest containing an "Ancient Tablet" that will allow you to enter "Lair of Ezul" at the final continent.

Hidden Skills:

- Gemeid Palace Dungeons (Acquire Meteor) Note: This is only available during the free-roaming stages of the game.

- Amanda Woods (Acquire Mending Stream)

Hidden Shops:

- Yvette's Shop at Fae Forest: Sells Stat boosts. (Enter the Gemeid Pub and open the chest containing a red wine, give the wine to the hooded figure sitting at the corner of the pub. He'll give you a key to open an old house in Fae Forest that has Yvette inside.)

- Troubadour Merchant: Sells Huge Stat boost accessory. (Gemeid Palace Dungeons) Note: This is only available during the free-roaming stages of the game.

- Hanni's Parents: Sells a rare power-up as well as potions. (You must take the second side-quest given by the Utania Mayor in order to avail this.)

- Eduardo's Shop: Sells rare potions. (You must take the third side-quest given by the Santa Cecilia mayor.)

Hidden Bosses/Weapons:

- Mt. Glacius (Acquire Dragon Sword by defeating the Winter Wyvern.)
- Zermo's Lair (Acquire Sorcerer's Ring by defeating the Inferno Wyvern.)
- Lair of Ezul (Acquire the strongest weapons in the game for each party member by defeating Ezul.)

That would be all, as far as I can remember! ^_^ Enjoy!