I’m not exactly sure what to call this architectural “thing,” but it’s basically a two story hole in the ground that alerts you of the massive underground network of government floorspace beneath the property of the Texas State Capitol.  The Capitol building itself is really just the tip of the iceberg. Center-to-center, this “hole” is about 500 feet from the capitol’s dome.  You can see it on Google Maps here.  And for those who love Wikipedia, here’s an excerpt from the article about the TSC: “To preserve the facade and historic plaza, the new capitol extension was built as a four-story underground structure, completed during 1993. Though the extension encompasses 667,000 square feet, nearly twice the floor space of the original building, there is little evidence of such a large structure at ground level, except for extensive skylights camouflaged as planter rows.”  Conveniently, they forgot to mention the structure seen below.  Enjoy!