Serra dos Órgãos was created in 1939 as the third National Park in Brazil. The objective was to protect the native forest on the hillsides and the fresh water springs abundant in the region. When created the park occupied land previously controlled by four municipalities: Petrópolis, Teresópolis, Guapimirim and Magé.
The Park's area is 110 km² and it has 10 peaks higher than 2000 m (6560 ft) and six other peaks over 1500 m (4920 ft) high. The lowest point in the park is located in the relatively flat municipality of Magé, at 145 m (475 ft). The highest peak is Pedra do Sino (Bell Rock), at 2263 m (7424 ft). Most famous formation in the park is the Dedo de Deus (God's Finger) rock, which resembles a left hand with its index finger stretched, pointing towards the sky. It is 1692 m (5551 ft) high and can be seen in the background of the of the Rio de Janeiro state, which appears in the center of the .
The park is part of the larger Serra do Mar chain of mountains, and the most accepted theory about its origin is that it rose about 60 million years ago during earthquakes that caused the Andes to rise. That means it is located in a geographically unstable location, although no incident has ever been recorded in the area.
Temperatures in the Hills can fall as low as 4 °C (39 °F), and the average temperature at 1000 m (3300 ft) is 17 °C (62 °F). Humidity is between 80 and 90% on average, but it can reach 99% at higher altitudes.