These are the 180 sources you can find in cities. Most will be locked behind storyline events (specially airship ones). You can now access the map from the in-game menu if you buy it on the shops, but gonna link it here for easier access. There's a interactive map on resources if you need too.

Shiokaze Pier

Futago Bridge

Gengetsu Lakeside

Extra notes

There's a total of 244 Sources of the Earth. Map shows you 180 sources, and the remaining ones are 60 in the sanctuaries (5 in normal and 5 in advanced per sanctuary), and 4 in Silent Valley.

• Some sources will be locked until Ring Sanctuary sequence (Adv. sanctuaries, floating sources and airship quests):

• Looking Down on "city"
• Airship flying around town 1, 2, 3
• Balloons disappearing into the sky
• Along the ... quests 1, 2
• Collect the fragments floating in the sky
• A little help

• There are 5 Sources that require 180+ Sources (200+ in a specific case) to be already picked up: 2 in Silent Valley, and one on each main city inside the "big building" on each area

• The remaining ones are obtainable after airship is upgraded in Twilight Sanctuary sequence, so basically after finishing the game. These ones are:

• Follow the Traces 1, 2, 3
• "In a hard, huge rock" 1, 2
• Destroy the relics of the earth (the big jars broken with bombs)
• Destroy the relics of the sky (the big jars broken with fireworks)
• Main Building NPC help quests (Paper pick up quests)