what is its interior like?
The Capitol building is marked by its central dome above a rotunda in the central section of the structure  containing the two original smaller meeting chambers for the Senate and the House of Representatives and then flanked by two further extended wings, one also for each chamber of the larger
United States Capitol
The Capitol building is marked by its central dome above a rotunda in the central section of the structure (which also includes the older original smaller center flanked by the two original (designed 1793, occupied 1800) smaller two wings (inner north) and inner south) containing the two original smaller meeting chambers for the Senate and the House of Representatives (between 1800 and late 1850s) and then flanked by two further extended (newer) wings, one also for each chamber of the larger, more populous Congress: the new north wing is the Senate chamber and the new south wing is the House of Representatives chamber. 
what is united states capitol cornerstone laying? It was the ceremonial placement of the cornerstone of the United States Capitol who designed this capitol building? William Thornton
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United States Capitol [SEP] Interior
The Capitol building is marked by its central dome above a rotunda in the central section of the structure (which also includes the older original smaller center flanked by the two original (designed 1793, occupied 1800) smaller two wings (inner north) and inner south) containing the two original smaller meeting chambers for the Senate and the House of Representatives (between 1800 and late 1850s) and then flanked by two further extended (newer) wings, one also for each chamber of the larger, more populous Congress: the new north wing is the Senate chamber and the new south wing is the House of Representatives chamber.