The San Isidro Cave is located in Santa Cruz in Marinduque Province. The San Isidro Cave, also known as the Bagumbungan Cave, was discovered by a team from the provincial tourism office and cave enthusiasts in 2009. The cave featuers the longest known Subterranean river in the province. San Isidro’s cave entrance is connected to Barangay Punong. A two kilometer route has already been mapped but many passages and chambers are still unexplored. The San Isidro cave features many waterfalls and unique cave habitats.