Thanks to a new coat of traditional lime wash Virginia's State Capitol has emerged from recent restoration as dazzlingly white as the White House in Washington. And after the removal of magnolia trees that shielded it from view it is once again seen in proud isolation as a temple on a hill.

The work is part of a $105 million transformation aimed at improving facilities and security for the smallest of the 50 working US state capitols, which attracts up to 170,000 visitors a year. Rather than add to the building, the architects have cut deep into the hillside immediate in front of the portico. With the use of modern technology the stability of building was constantly monitored by French engineers at their desks in Paris.

Thomas Jefferson, the author of the Declaration of Independence and later the 3rd President of the United States, received the invitation to design the Capitol in 1785, two months after he arrived as ambassador in Paris. Jefferson seized the opportunity to show how public buildings in America should be inspired by the finest examples of ancient Greek and Roman temple architecture. His design, with a columned portico at one end only, has long been recognised as based on the most famous Roman temple in France, the Maison Carrée in Nîmes.

Jefferson described this as “the most perfect and precious survival of antiquity in existence” and superior to “any thing at Rome, in Greece, at Baalbec or Palmyra”. He also noted that the Ionic columns he chose (unlike the Corinthian ones in Nîmes) were modelled on those on the entrance to the Erectheum in Athens.

Jefferson had his plans elegantly drawn up by the French artist Charles-Louis Clérisseau. The original architectural model made in France by Jean-Pierre Fouquet is preserved in the Capitol. The detail had been obscured by successive coats of paint applied to the model to correspond with the outside of building each time it was repainted. Careful removal of layers of paint on the back of the model have documented successive changes of colour from cream, to biscuit and a battleship or Confederate grey. Rather than strip the whole model conservators decided to build a faithful replica to display Fouquet's proposed carving and ornament.

Jefferson's Capitol was extended in 1906 by J Kevan Peebles and William C Noland with lower, balancing wings, each with handsome shallow four-column porticoes on three sides. Within, they contained new chambers for both Senate and House of Delegates. Jefferson's original House of Delegates remains at the back of main building.

The Capitol was built of brick faced in stucco and the six white columns contain the original pine tree cores. The portico was initially built without the external steps Jefferson intended. Samuel Dobie, the contractor, had decided that Jefferson's proposal to place offices on the top floor would have rendered them unbearable in the summer heat. Instead he placed them on the ground floor where windows were introduced in place of Jefferson's proposed steps.

The new submerged ascent, designed by George C. Skarmeas of RMJM Hillier Architects, complete with committee rooms and exhibition gallery, takes the form of a grand processional stair with a complementary succession of ramps and lifts which make wheelchair access a ceremonial event in itself. Visitors emerge from the extension into the central galleried hall, which has a striking resemblance to the great hall at the Queen's House in Greenwich, and even more to that at Houghton Hall in Norfolk which Jefferson would have known from engravings. Instead of a flat ceiling Dobie introduced a dome allowing light to stream into the hall which is without external windows.

In the centre stands a superb marble statue of George Washington by the great French sculptor Jean-Antoine Houdon. Jefferson persuaded him to travel to America to take detailed body measurements of the President at Mount Vernon, making sketches as well as a life mask. Standing 6ft 2 it was considered from the start a perfect likeness.

The historian Ramin Saadat has suggested that the idea of making the Richmond Capitol a shrine to Virginia's foremost statesman is based on Euhemerism, a theory popular in the 18th century. Euhemerus, a 4th-century Greek writer, argued that the ancient gods had in reality been mortal leaders whose veneration had turned to worship as myths grew in the telling.

One big question was whether the new entrance at the bottom of the hill should be lined up on Jefferson's portico. The solution, proposed by Calder Loth, an architectural historian to the state Landmarks Agency, is based on the Greek Doric Temple of Temperance which is set at a picturesque angle below Bremo, one of the handsomest Jeffersonian country houses in Virginia. When planting has taken hold in the Texas limestone walls flanking the new entrance it will look like a verdant grotto.

The Capitol is open to visitors Monday-Saturday 8.30am-5pm and on Sundays 1pm-4pm. Visitors may explore on their own or join a guided tour.

www.virginiacapitol.gov