|The only picture I found of the construction.|
Digging a hole in sold rock can be a bit of a challenge for most people, but not the Texas legislature. They wanted to expand their office space, but they did not want to block the view of the capitol building, so they elected to build it underground, carving a giant hole out of solid rock.
|Texas State Capitol building section through light courts, north view.|
|Texas State Capitol and Extension building section looking west.|
|Skylights for the underground Capitol Extension|
In 1993, the $75 million, four-story, underground Capitol Extension was completed to the north, doubling the square footage available to Capitol occupants and providing much improved functionality. 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, and the four-story open-air inverted rotunda. - Wikipedia