The Mayans were located in the Mexico in 2600 B.C.
Another achievement would be the number system
One of the achievements are making the calendar because we still use it today.
Slash and burn
Another achievement they had was making tires and we also still use them today
The end of the civilization
If the Mayans never created the number system than we wouldn't have most of the stuff we have, like money,jobs, schools, cars, and many more.
My theories of why the Mayan civilization ended are the slash and burn, the wars they constantly fought, and the winter snow might have got frost bit and die. What I think happens next is that someone else took over their civilization and they were peaceful.
The Mayan civilization ended because of the collapse and they disappeared but know one knows what happened to they. My theory of why the civilization ended is all the wars they had to keep them company.