One of the factors that lead me to investigate the possibility of ancient advanced civilizations were several visits to what is now known as the Crystal River Archaeological State Park in Florida.
Having two (2) of the only known stone steles in Florida (or U.S.,) the park has a proposed link to the Maya civilization on the other side of the Gulf of Mexico. Stele #1 has been dated to 440 CE, which is prior to the collapse of the Mayan civilization, so the people that raised this monument were not the remnants of the survivors.
Stele #1 is even inscribed with a face that is slowly fading from exposure to the weather. The view shown here is looking towards the northern temple mound.
Stele #2 points to the north temple mound at the site in this view, as well as forming the observation point for the astronomical alignments.
Looking from Stele #2 to Stele #1 shows the alignment with the Winter Solstice at sunrise.
Research and excavation has shown this to have been a ceremonial site with few occupants, except possibly during special periods. The site has been thoroughly excavated, but there are other sites in the vicinity that one day yield more evidence about their connections to the Maya and maybe other peoples who had a deeper understanding of our world.
Have a great day.