Luxembourg Palace. The gray, imposing Luxembourg Palace was built, like the surrounding Jardin du Luxembourg, for Maria de' Medici, widow of Henri IV, at the beginning of the 17th century. Maria was born and raised in Florence's Pitti Palace, and having languished in the Louvre after the death of her husband, she was eager to build herself a new palace where she could recapture something of the lively, carefree atmosphere of her childhood. In 1612 she bought the Paris mansion of the duke of Luxembourg, tore it down, and built her palace. It was not completed until 1627, and Maria was to live there for just five years. In 1632 Cardinal Richelieu had her expelled from France, and she saw out her declining years in Cologne, Germany, dying there almost penniless in 1642. The palace remained royal property until the Revolution, when the state took it over and used it as a prison. Danton, the painter David, and Thomas Paine were all detained here. Today the French Senate meets here, so the building is not open to the public. However, next to the palace is the Musée de Luxembourg (PHONE: 01-42-34-25-95; www.museeduluxembourg.fr). Once home to many of the masterpieces now on view at the Musée d'Orsay, it is open occasionally for temporary exhibitions. Its shows have proved very popular, so you should anticipate a line; recent exhibits have included Sandro Botticelli and, in autumn 2004, Paolo Veronese. Métro: Odéon; RER: Luxembourg.