So all this time I imagine that Michael Heizer's Double Negative, dug into the edge of Mormon Mesa, is like the lost earthwork, no one can get to it, no one can find it, &c., &c.
Turns out the thing's an hour outside Las Vegas, like 15 minutes from cheery downtown Overton, which is an exit on I-15. At least I assume downtown Overton's cheery; we didn't actually make it that far. Turned off by the airport, took Mormon Mesa Rd. across, then turned left onto, uh, Double Negative Way, just before the cattle guard.
If Spiral Jetty was this easy to visit, there'd be a day spa there by now. Or at least a Cracker Barrel.