Hidden gem

n.joyful, thoughtfulwarm

What it means

An excellent person, place, or thing that has not received broad recognition.

Reach for it when recommending overlooked quality without pretending the discovery is secret

The volunteer-run cinema is a hidden gem with thoughtful weekly programs.

playful
best-kept secret
insider knowledge gives the recommendation charm
not when The phrase can encourage crowding and falsely imply deliberate secrecy.
playful
sleeper
something initially overlooked later proves unexpectedly successful
not when Sleeper often concerns commercial performance and can sound odd for a person.
everyday
find
the recommendation is pleasantly surprising
not when Find centers the recommender's discovery and says little about enduring quality.
warm
unsung talent
a capable person deserves recognition for overlooked work
not when Unsung talent applies to people and abilities, not secluded places or products.
literary
overlooked jewel
beauty and value have escaped broad notice
not when Jewel is ornate and can overstate a modest but worthwhile experience.
literary
undiscovered treasure
exceptional value awaits wider appreciation
not when Undiscovered is false once a community already knows and sustains the place.

local hidden gem
The local hidden gem limits group size to protect its small garden.
true hidden gem
A true hidden gem earns praise from evidence, not merely low visitor numbers.
discover a hidden gem
Readers can discover a hidden gem without treating residents as scenery.
hidden gem restaurant
The hidden gem restaurant is already well known to its neighborhood regulars.

Calling a place a hidden gem can erase the community that already values it and can accelerate unwanted crowding.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.