Cerro Santa Lucía is a hilltop park located steps from the Biblioteca Nacional on Alameda and Santa Lucía. It's open daily 9am to 8pm from September to March, 9am to 7pm from April to August; admission is free. The Mapuches called this rocky hill Huelén (Curse) until Pedro de Valdivia renamed it Santa Lucía in 1540. In 1872, the area was expanded to create walkways and small squares for the public's entertainment, and now office workers, tourists, couples, schoolchildren, and solitary thinkers can be seen strolling along leafy terraces to the Caupolicán Plaza for a sweeping view of Santiago. The plaza also serves as the site of theater and concerts in the summer.
Continue along the garden walk to Castle Hidalgo, built in 1820 and now an event center. To get to the top, begin at the stone monument staircase on Santa Lucía and O'Higgins, or take the glass elevator up a bit farther on Santa Lucía. Keep an eye open for suspicious characters if you choose to climb up at sunset. At the staircase you'll also find the Centro de Exposición de Arte, with a large assortment of Indian-influenced crafts, clothing, and jewelry on display and for sale. Across the street is a bustling crafts and junk market, the Centro Artesanal de Santa Lucía, with handicrafts, T-shirts, and more.
Behind the park, at José Victorino Lastarria 307, you'll find the Plaza Mulato Gil de Castro (closed Sun). Named for the 18th-century Peruvian Army captain and portrait painter José Gil, who lived in the neighborhood, this quaint plaza is a great place to explore, grab a cup of coffee, or have lunch. The plaza sits in the middle of a historic neighborhood built of beautiful stone mansions and boasts an excellent Museo de Artes Visuales (open Mon-Sun 10:30am-6:30pm, $1.40 admission). The art museum displays an impressive amount of sculptures, photography, and paintings by Chilean artists.