The area of 285.44 km2 (28,544 ha) between 3100m and 4450m above sea level is characterized by páramo vegetation on a jagged landscape of hills and valleys.

[3] The highest point is the 4,450 m high Cerro Arquitectos (Architects Hill), and the elevation of roads reaches higher than 4,310 meters (13,550 feet).

As the park straddles the continental divide, its western drainage, the Balao and Cañar link to the Pacific ocean.

Clouds typically drift up from the Pacific coast and from the Paute river basin (near Cuenca) and bring humidity.

Humidity and high altitude with low atmospheric pressure create an ecosystem that accumulates organic material in the soil that is able to retain water.

It is in forests such as these that a second protected population of the rare Fuchsia campii, in the family Onagraceae, is predicted to live, as it has also been found in another nearby national park of similar ecological characteristics.

The Cajas National Park is home to a large variety of animals, some of which are endemic or highly endangered.

Endemic are the Cajas water mouse (Chibchanomys orcesi) that belongs to the group Ichthyomyini and Tate's shrew opossum (Caenolestes tatei).

A road from Chaucha to San Joaquin touches on the southern border of the park providing access.