In 2012, a major restoration of the native habitats in the El Polin area was completed with the help of many community volunteers.
El Polin spring water bubbles from a serpentinite rock wall at the head of this riparian valley. The spring provided a source of fresh water for the Spanish Presidio occupants, and this sheltered valley was the first location that Spanish families built their homes outside the Presidio walls. Later, during the Spanish American War of 1898, the First Tennessee Volunteer Infantry Regiment camped here, providing the name Tennessee Hollow to this valley. Today, you can picnic near the spring or explore the surrounding scrub and grasslands which are home to many plant and bird species.