The Palacio de La Moneda (Mint Palace), has two large open spaces; a small pool and fountains in the front (Plaza de la Ciudadanía), and small park in the rear. The former mint (hence the name), was built in the early 1800s and since 1952 is where the presidential offices are located. There isn’t much to do at the Mint Palace itself, although you can catch a changing of the guard at 10am on most days. Otherwise you can head down to the free cultural center underneath La Moneda and take a look at various art and history exhibits.
Santiago is a wonderful city for strolling and from the Palacio de La Moneda you can easily get to some other popular touristic areas like Plaza de Armas. In fact, most of Santiago’s sights that travelers might be interested in are within walking distance or quick metro ride of each other.
You can see a few more of my pictures from Santiago here.