Returning to Nibelheim
The town of Nibelheim, which is Tifa and Cloud’s hometown, is host to a number of different side quests that are available at different points in time throughout the game.
Your first visit to Nibelheim is during the flashback cutscene when the team arrives in Kalm. Make sure that you travel into Tifa’s house and that you attempt to play on her piano (choose to try and “jam on it”).
The second time you encounter Nibelheim is when your team actually travels there. Aside from a host of items that are available in and throughout the town, this is also the first time that you can complete the side quest to obtain Vincent, one of the optional / secret characters. Check out the Secret / Optional Characters section under Vincent for more information.
Disc 2 Visit
You can visit Nibelheim again as soon as you obtain the Highwind after escaping from Junon. Revisit the town and, if you chose to jam on Tifa’s Piano during the flashback sequence in Kalm, you will now be able to obtain an Elemental Materia by playing Tifa’s piano again.
This next portion can only be completed once Cloud has returned to your party but can also be completed in Disc 2. If Cloud has not yet joined your party you must wait before doing this portion of the side quest. Add Tifa to your party and travel to her house and choose to play Tifa’s Piano up in her room. Play the following tune (which is the main theme song from the World Map):
A scene will start up and at the end of it you will receive Tifa’s Level 4 Limit Break, Final Heaven.