Baldassare Forestiere carved the Forestiere Underground Gardens in Fresno, California, over 40 years from 1906 to 1946. The subterranean complex spans 10 acres and contains 65 rooms, including kitchens, baths, and a fishpond. He used only hand tools and mules, avoiding any formal plans.

The gardens rely on precise airflow engineering: conical skylights and narrow passages push hot air upward while cooler air stays below. Hardpan excavated from the site became bricks for arches, and displaced soil built planters and terraces. The design protects fruit trees from winter frost, extending the growing season.

In 1977 the site earned place on the National Register of Historic Places, followed by California Historical Landmark status in 1978.