In the southeast of the state, the National Park of Serra da Capivara is a UNESCO World Heritage Site.

The park has more than 400 archaeological sites and the largest concentration of rock paintings in the world, in a landscape dominated by canyons and caatinga.

Early settlers in the region included Francisco Dias d'Ávila from state of Bahia,[4] who brought the first herds of cattle to the area; and Domingos Afonso Mafrense, from Portugal, who founded what is today Oeiras.

Large estate owners seeking new pastures for their livestock arrived from neighbouring states such as Bahia and Maranhão.

At the beginning of the 20th century, the principal industry of the state was stock raising, which dates from the first settlement in 1674 by Domingos Afonso Mafrense, who established a number of cattle ranges.

This plateau region is watered by numerous tributaries of the Parnaíba, chief of which are, from south to north: the Poti, which has its source in the state of Ceará; the Longa; the Canindé and its tributary the Piauí, which is navigable for boats of one-meter draft up to Nova Iorque, a few miles above the mouth of the Gurguéia River.

[5] The river valleys are separated by flat-topped plateaus called chapadas, including the Serra Uruçui, which lies between the Uruçui-Preto and the Gurguéia, the Serra da Capivara National Park, which lies between the Gurguéia and the Piauí, and the Chapada das Mangabeiras, which forms the southwestern boundary of the state, separating the upper basin of the Parnaíba from that of the Tocantins.

The sandy soils along the Atlantic coast are home to the Northeastern Brazil restingas, low evergreen forests adapted to the nutrient-poor conditions.

The Cerrado savannas extend across the southwestern portion of the state, in the basins of the upper Parnaíba and Gurguéia rivers.

Enclaves of Atlantic dry forests lie in basin of the Gurguéia, forming a transition between the Cerrado and Caatinga.

The climate is hot and humid in the lowlands and along the lower Parnaíba, but in the uplands it is dry with high day-time temperatures and cool nights.

Piauí exports include essential oils 19.5%, soybeans 17.1%, woven cotton 15.1%, cashews 12.6%, crustaceans 12.4%, and leather 8.3% (2002).

Diamonds are mined by Gema do Piauí Mineração Ltda (Gemapi) and processed in the neighbouring state of Pernambuco in a joint-venture with Gitanjali Group (India).

Festa Junina is a cultural festival inspired by Portuguese traditions, in which St John's day, on the June 24, is one of the oldest and most popular celebrations of the year.

During these fifteen days, there are bonfires, fireworks, and folk dancing in the streets (step names are in French, which shows the mutual influences between court life and peasant culture in the 17th, 18th, and 19th-century Europe).

[citation needed] The four-day period before Lent leading up to Ash Wednesday is carnival time in Brazil.