when I last visited the Angkor ruins, I seem to recall reading/hearing that there are still a lot more there still to be discovered (sorry, no cite).
Octopuses clearly have substantial mechanical problem solving abilities and a great curiosity; however, it is unclear how great their communication skills are in the context of a natural language and they are not social animals that form into herds or tribes the way primates, elephants, many birds, et cetera do. Squid are also intelligent and most species do collect in groups (I’ve said ‘schools’ in the past but was informed by a marine biologist that this is inappropriate nomenclature as cephalopods are not fish) where the often communicate for both hunting and breeding purposes but have not shown any kind of tool use. All cephalopods have relatively short lives—most dying sometime after a single spawning—and do not rear their young so it seems unlikely that they will evolve to transfer abstract knowledge from generation to generation although octopus can clearly learn by observing one another.
If I were to look for some aquatic class to have developed an advanced society that would disappear without a trace it would be in Cephalopoda but there is nothing in the evolutionary record that suggests that this ever would or could have happened.
Most of the non-temple buildings were constructed out of wood and textiles, and because of the wetland environment that they were constructed in perished without maintenance or replacement. There are doubtless some ruins remaining preserved in bog-like depressions in the area because it was continually occupied several hundred years but nothing that would be considered intact and excavating them would disturb the wetland areas and the ecology around them, so most excavations have been limited to in and around the Angkor moat. There are, of course, other Buddhist temples of comparable complexity if not scale found all around Southeast Asia (most notably Bagan in Myanmar and Borobudur in Indonesia) and doubtless many undiscovered sites of the truly ancient (i.e. pre-European Classical Antiquity era) societies but nothing that would be considered intact or containing great treasures and diabolical traps that an intrepid fortune hunter would have to disarm to find an eldritch artifact capable of destroying entire armies if not securely lost in an anonymous crate in a giant warehouse.
Stranger
Well that sucks…
Better than having your face melted off for the sin of being curious.
Stranger
Did a double-take when I thought this said the Mayan Punic style of architecture. Hitherto unknown civilizational crossovers!
I don’t think the Nazis’ sin was curiosity.
Yeah but the seraphim emerging from the Ark are indiscriminately attacking anyone who is not averting their eyes; hence why Indy tells Marion: “Don’t look at it. Shut your eyes, Marion. Don’t look at it no matter what happens.” Good or bad, if you look into the Eyes of God through His representatives you are going to get your face melted off. (It also is a reversal of Indy’s earlier monologue to Marcus Brody about his lack of belief in “superstitious hocus-pocus” about the Ark.)
Stranger
Hey. No skeptics in a tomb, amirite ?
So far, we have:
Look into the eyes of God: face melts
Hear the voice of God: mind caves in, heart explodes
Anything else?
Has anybody actually looked for that?
When drinking from a chalice, choose wisely.
Stranger
For layers in the strata containing unusual concentrations or combinations of elements? Sure, that is how the iridium layer associated with the K-T boundary was identified.
Stranger
I thought Bosda was asking about that object which according to some sources is being kept in the basement of some church in Ethiopia 
A new complex of Neolithic buildings was discovered in 2003 in Orkney at the Ness of Brodgar;
the excavations for the UK’s new high-speed rail line has found a fascinating Roman cemetery, with 40 beheaded skeletons (perhaps to stop them becoming zombies?)
There are fascinating discoveries being made every day. I am sure there is plenty of archaeology from the pre-Columbian era still to be found in the USA, including some pretty impressive earthworks.
I’d look for flint tools first. Flint tools seem like a reasonable first stage of development, and they would last practically indefinitely in sedimentary deposits (at least until metamorphosis occurred). Since there are no out-of-place flint toolkits from the Mesozoic, I’m fairly confident that dinosaurs never developed any easily recognisable technology.
There are Indian Mounds within the US and Canada that may be undisturbed.
It wouldn’t be allowed to open them now. It might be possible to use non-invasive tech to scan the interior.
We have a State Park that features an Indian Mound.
A group of squid is a squad. Or should be.
Stone tools do seem likely for mechanical tool users (which is likely that any terrestrial vertebrates would be) but after millions of years they would be subsumed into the substrate and mostly crushed or compressed into other strata. We can be confident that “dinosaurs” (an expansive term that actually covers an expansive range of polyphyletic species that should probably occupy multiple clades) were not tool users simply because the fossil record does not show any anatomy consistent with sophisticated tool manufacture and use, i.e. no evidence of grasping appendages, and ‘modern dinosaurs’ have evolved their upper appendages for flight rather than manipulation. If a species developed from dinosaurs to expand even as far as prehistoric humanity with that kind of capability we would expect to see something in the fossil record of it and/or its predecessors even if it did not leave any residual substances or tools.
The North American mound builders (probably multiple pre-Columbian cultures but predominately identified with “Mississippian” culture most closely associated with the extant Caddo Nation) built earthwork mounds without any internal structure, and indeed, even the unmutilated structures have suffered from slump of the soil. They likely had structures built atop them of timber or small stone but probably decayed or were removed for salvage following the North American Native Genocide, and most mounds were plowed over by farmers to make the land suitable for pulse agriculture without revealing any treasures or complex interior structure.
Stranger
I thought the mounds were similiar to the South American temples.
Thank you fot setting me straight.
I think the one in your picture there is Poverty Point, which IS a remarkable site. There is no stone architecture under there (there’s not much stone anywhere near there, really) but it was a tremendous settlement that predated agriculture by millenia. They moved enourmous amounts of dirt to contstruct a planned community.