The desert tortoise intaglio is located near Barstow, California.  There is not much known about it, but it is considered to be quite old and has been documented for several decades.  It’s in an area of the Mojave desert where there are several well known ancient & prehistoric rock art locations.  The design itself is roughly 40′ across, with a line going through the middle of the body (perhaps an arrow, or a spear?).  After much study and research by John Rafter, it’s best believed that this is a form of archaeoastronomy (a method of aligning to key stars, constellations, sunsets & rises, etc.).  Mr. Rafter confirmed the head points due north and the legs align to the equinox.  Based on the assumed age and the inhabitants at this time, the best guess is that this was created by the Chemehuevi people.  Right next to the intaglio are two small groupings of rocks: one in the form of an hourglass-like shape, and another in the form of a ring at the end of one of the legs of the tortoise.

From: https://www.talesfromthedesert.com/portfolio/desert-tortoise-intaglio/