Sant Andrea al Quirinale is located high on the Quirinal Hill, on the Via del Quirinale, on a rectangular site with its long side facing the major avenue. Now major avenue in Rome means two lanes and sidewalks, mind you. It is the masterpiece of church design of Gian Lorenzo Bernini, who attended the church, claiming it was his only perfect work. The genius of his design is his creation of an optical illusion of a normally proportioned church sitting in what is in reality an awkward location.
The interior is stunning, and greeting the visitor straight ahead is a miraculous vision of the apostle Andrew being borne into Heaven in a blaze of stuccoed glory.
Above, you can see his martyrdom in paint, where the apostle continued to preach on an X-shaped cross even after being pardoned by the Roman governor. Below is a close-up of the stuccoed figure of St. Andrew.
Below is the hidden window that Bernini used to light the altar; he always hid his light source to give the impression that Heavenly rays were falling on the miraculous vision.