You're referring to the classic game "Roads of Rome" and its New Generation 3 installment!
Below are general cache locations and specific spots revealed for various levels: Common Cache Types & Locations
Level 13–15: These levels each contain 4 caches, requiring a keen eye to spot before the timer runs low. Episode 3: The Deep Forest Level 21: Features 4 caches. Locations include:
- Immediate Resource Injection: A clutch of rare materials (marble, glass, or early steel) that can bypass a production bottleneck.
- Meta-Progression Currency: Shards of “Legacy Tokens” used to unlock permanent passive bonuses for subsequent levels—faster walking speed for builders, reduced tool degradation, or extended rally point range.
- Environmental Storytelling: The cache’s location often tells a micro-story—an abandoned surveyor’s chest near a collapsed aqueduct, a legionary’s lockbox half-swallowed by a cursed swamp, or a merchant’s stash hidden behind a waterfall that only appears when you divert the river.