buried, hidden, lost, sunken
pirate, royal
vast
a vast treasure of medieval manuscripts

hunt for, look for, search for
dig up, discover, find, uncover, unearth
steal
bury, hide

chest, house, trove (figurative)
This book is a treasure house of information on Arctic birds.
The book is a veritable treasure trove of information.

map
hunt, hunter, hunting

a hoard of treasure

great, precious, priceless, valuable
rare
ancient
forgotten, hidden, secret, unexpected
Many forgotten treasures have been discovered in old houses.

archaeological, architectural, historic, historical
art, artistic, cultural
family
national

discover, find, uncover, unearth