The church of Sant'Agnese in Agone was built on the place where, according to tradition, Sant'Agnese was exposed naked to the pillory and was covered with her hair miraculously untied. The present construction was started by Girolamo and Carlo Rainaldi in 1652, under the papacy of X, and completed by Borromini (1653-1657), who remarkably modified it. 

One owes to this super artist the concave façade with a single order of pilasters as well as the columns and the high couple. The twin bell-towers were carried out by Antonio del Grande and Giovanni Maria Baratta, according to a plan by Borromini. 

The inside, by Rainaldi, saves the Greek cross plan and hosts splendid golden and marbles works by Borromini. The dome, surmounted by eight columns, was frescoed by Ciro Ferri helped by Baciccia. In the underground one can admire the ruins of the Circo di Domiziano, the mosaic floors and splendid medieval works on the walls.