Oaxaca's main square – formally referred to as the Plaza de la Constitución de Oaxaca, but colloquially called the Zócalo – is a must-see. Skirted by cafes and eateries and bounded by the Palacio de Gobierno (the State Government Palace) on its south side, the Zócalo is a prime spot for people-watching, picking up a souvenir or two and watching day fade into vibrant night. Thanks to its leafy landscaping and many trees, it's also a relaxing place to cool off in the shade. Plus, the Mercado Benito Juárez sits just minutes from the square. 

Recent visitors gushed about the Zócalo, saying it's a nice spot for an afternoon coffee or an evening margarita. Others suggested visiting at night when the Zócalo fills with live music. You'll find the Zócalo in the heart of Oaxaca; it is free to enjoy at all hours of the day (though businesses operate on their own hours). For more information, check out Visit Mexico's website.