What would last of humanity on Earth
I highly recommend the book The World Without Us by Alan Weisman.
See the excellent Web site, which includes an animation of how
long our homes would last without us (not too long at all in a
geological time frame):
http://www.worldwithoutus.com/
The Pyramids of Egypt are estimated to last about 125,000 years.
The only things made by humans that will truly survive for ages
are the deep space probes. The Voyagers and their Interstellar
Records, for example, may last one billion years or more. Of course
even that is just a fraction of how long the Universe as a whole
will last.