If you're driving between Riverside County and Los Angeles over the next 11 nights, be on the lookout for a 340-ton megalith.

The granite boulder, 21½ feet tall and wide, will be part of Michael Heizer's monumental work Levitated Mass, which will be installed at the Los Angeles County Museum of Art once the boulder arrives. It will travel 105 miles on a custom-designed transporter from the quarry near Riverside through four counties and 22 cities. A map of its travels is available at http://www.lacma.org/levitated-mass-map.

Imagined four decades ago, Heizer's project will place the boulder over a 456-foot-long slot in the museum's lawn, so that to those walking through a trench beneath, the stone will appear to hover in air.

As reported in A.i.A.'s October 2011 issue, the transport was originally planned to take place between September and October, but finally begins tonight and will take place between 11 pm and 5 am.