In addition to supervising the construction of the Capitol extensions in the 1850s, Captain Montgomery C. Meigs directed plans for the new interior spaces of the building. In December 1854, Meigs met Italian artist Constantino Brumidi, a master of buon fresco (true fresco), a difficult technique in which mineral colors and water are rapidly applied to fresh mortar and allowed to dry as part of the wall. "He is full of genius and talent, [and] designs with a fertility which is astonishing to me," Meigs wrote after hiring Brumidi to work on the Capitol. Brumidi assembled a team of artists and painters of many nationalities to execute his designs for the Capitol and its new Senate wing. The artist spent the next 25 years decorating the Capitol. His murals can be seen in numerous rooms and corridors throughout the building. The centerpiece of the Capitol Rotunda is his allegorical painting, The Apotheosis of George Washington.