This is actually the backside of the Capitol building. In this photo you can see the underground building and how they have artfully hidden the skylight with hedges.
"In 1990, work began on the Capitol Extension, an underground building designed to provide the Capitol with much needed additional space without sacrificing its historical integrity. This monumental project which involved digging a 65-foot-deep site out of solid rock, provided the Capitol with approximately 667,000 additional gross square feet and was completed in 1993."
One thing I love about the Capitol building is that it is made from pink granite which makes it a little unique!