Archaeological Bulletin 38: Peru found the earliest observatory on the American continent to date (Changiro Chankillo) dating back 2300 years. Archaeological Bulletin 38: Peru found the earliest observatory on the American continent to date (Changiro Chankillo) dating back 2,300 years. Archaeological Bulletin 38: Peru found the earliest observatory on the American continent to date (Changiro Chankillo) dating back 2,300 years. Archaeological Bulletin 38: Peru found the earliest observatory on the American continent to date (Changiro Chankillo) dating back 2,300 years. Archaeological Bulletin 38: Peru found the earliest observatory on the American continent to date (Changiro Chankillo) dating back 2,300 years.