I was riding along on a Honolulu city bus when I noticed an huge black pipe construction in a park along King St., just down the street from city hall. I snapped a couple of quick photos, and eventually figured out what it was after a bit of google-fu. This is Skygate, a 1975 sculpture by Isamu Noguchi, who is probably best known for designing the iconic midcentury Noguchi table. The city arts page for it has a brief description:
An abstract nonrepresentational steel sculpture composed of three equidistant straight steel pipe legs connected at the top by a horizontal undulating tubular form. The steel of the sculpture is painted black overall. At groundlevel at the center, the space is defined by a stepped two-part circular concrete platform. Located at the Honolulu Civic Center.
What this description doesn't tell you is that Skygate also figures in a fun astronomical phenomenon. You may have heard of New York City's "Manhattanhenge", the twice-yearly event in which the setting sun aligns with the Manhattan street grid. In Hawaii's twice-yearly Lahaina Noon, the midday sun appears exactly overhead, such that a flagpole (or a person) casts no shadow. At this time, Skygate casts a shadow directly beneath itself, forming a perfect ring on the concrete circle below. This typically happens in May and again in July. I was there in September, though, so I couldn't have seen it even if a.) I'd gotten off the bus, and b.) I'd known about this phenomenon when I was over there. I mean, this isn't exactly the Map Room scene from Raiders of the Lost Ark; you'll get a roughly similar shadow any time of year, it just won't be perfectly circular or aligned with the concrete disc beneath. So it's admittedly less spectacular than the movie, but you also don't need to go to Nepal first to fetch the headpiece of the Staff of Ra before Hitler's minions find it. So there's that.
A 2008 Honolulu Magazine story has a photo of Skygate at Lahaina Noon, and a July 2005 Star-Bulletin article includes a photo with the ring a bit off-center, probably from a few days to one side of a Lahaina Noon. I also ran across someone's pinhole camera photos of a Lahaina Noon in May 2010; the photos demonstrate that the shadow is circular even though the center ring of the sculpture itself is sort of triangular. The third photo includes the city's then-mayor photobombing the shot.
An article at DesignIntelligence points out that Noguchi was an associate of Buckminster Fuller, who had created an early (and now demolished) geodesic dome for the Hilton Hawaiian Village in Waikiki.
Wisely, Bucky and his associates on geodesic dome structures (sculptor Isamu Noguchi and structural engineer Shoji Sadao) decided to create a very special unprecedented work-of-sculpture for the landscaped oasis surrounding state and city government buildings. It symbolically resembles one unpaneled hexagonal spine structural system within a typical geodesic dome that was planted in the mid-‘70s. On an AIA Honolulu city walking tour, I spent more than 20 minutes at Noguchi”s “Skygate” with a group of perceptive and knowledgeable chemical and bio-phys-chemical engineers who were vitally interested in the geometrical assemblage and fascinated with its imagineering, macromolecular architectural form and content.
A 2012 Durability+Design article about art conservation efforts on Skygate claims it has "astrological" significance, and asserts that the sculpture is the only place in the US where the sun ever stands directly overhead. This is not actually true; Lahaina Noon happens all over the inhabited Hawaiian islands, though the dates vary by a few days from location to location. The US mainland is too far north to ever have the sun directly overhead, however. In sort of the same vein, a few years ago a local contemporary dance company performed a piece beneath Skygate, and the description goes on about the sculpture's "sacred geometry", whatever that is. It's a cool and interesting design, and personally I don't see how dreaming up supernatural mumbo jumbo about it really adds anything of value. Although I did find a vintage photo of Vincent Price posing next to Skygate, believe it or not. A celebrity endorsement like that has got to be worth some serious mystical street cred.