Also located South-west of the Bahoruco Peninsula is Bahía de las Águilas (Bay of Eagle's), a bay which stretches out 8.5 km in length, 5.4 km of which constitutes beach area in its central region, and is a highly protected part of the Biosphere-reserve for its concentration of endemic and endangered species like The Hispaniolan Solenodon, The Hutia (Hutia Conga), and Rhino Iguanas.

The geological formation of the Bahoruco Mountain Range rests atop sedimentary limestone and marl-stone from the Eocene and Pliocene eras, which contain various species of algae, and is at its base supported by volcanic rock from the caribbean plateau.

Sierra de Bahoruco is home to one of the most emblematic sites on the Bahoruco Peninsula, El Hoyo del Pelempito (Pelempito's Hole), located 361 meters below sea level, Pelempito is the product of a collapsing of cave systems below its surface millions of years ago, due to pressure from underlying tectonic plates.

El Hoyo del Pelempito has a width of 2.5 kilometers and length of 7 kilometers, forming a triangular shaped depression with an oscillating temperature of 15 to 25 degrees Celsius, while the surrounding border mountains can reach up to and surpass 1,800 meters in height.

The park is home to several threatened species, including bay-breasted cuckoos, Hispaniolan amazons, the least poorwill, white-necked crows, western chat-tanagers and La Selle thrushes.