Sonic Frontiers

Challenges are marked by a red icon with a symbol that looks like a question mark (The same one seen in the trophy icon). Challenges are small puzzles/tasks you must complete in order to reveal more of the map of the current island, and also create rails to travel easier around the map. Usually by finding challenges, and revealing the map, you will in turn find more challenges to reveal more of the map. If the map is incomplete, and no challenges appear on the map, look around the unexplored sections of the map to find the challenges you are missing. Thankfully, they have nicely sized markers in the open zone that are easy to spot when you are close, so this should not be too difficult. Be aware that some challenges can only be done at night. This is indicated by an icon with a moon and star next to the challenge.

Look below for a fully revealed map of Kronos Island: