CORREGIDOR - Of the five islands at the entrance to Manila Bay, Corregidor is the largest, with an area of 1,735 acres. It is a rock formation about 4.0 miles long which lies two miles and seven miles, respectively, from the shores of the provinces of Bataan and Cavite. Corregidor, which was renamed by the Americans as Fort Mills, divides the mouth of Manila Bay into two channels, called earlier by the Spaniards as Boca Chica (Small Channel) and Boca Grande (Large Channel). These two channels were subsequently renamed by the Americans as the North and South Channels.

From the air, Corregidor resembles a tadpole with its head thrusting into the South China Sea, and its body and tail curling east and south back into Manila Bay. Some geologists claimed that the island used to be a part of a huge volcano that erupted on one side and gradually eroded to disappear partially beneath the sea.

The terrain in its round head rises to 628 feet at its highest point which is the site of a lighthouse built originally by the Spaniards in the 1830s. It flattens into two plateaus called Topside and Middleside and the Bottomside is almost at sea level. The island's summit affords fine views of the rugged coast of Bataan and the surrounding sea and at its tail end are narrow sandy beaches. Although Corregidor is only about thirty miles from Manila, it is a few degrees cooler with cool offshore winds which bring a welcome relief especially during the dry season. Shrubs and flowering trees abound. There are fire trees, bougainvilla, hibiscus, palm trees, cadena de amor, and orchids bloom amid the branches of trees. The vegetation somehow enhances the tropical appearance of the island.

CABALLO - Located on the South Channel and about 2.6 miles east of Corregidor is Caballo Island which is also referred to as Fort Hughes. It has an area of seventy-five acres and when viewed from the lighthouse on Topside of Corregidor, the island appears as a wedge of rock jutting out from the sea. The island is now used as an installation of the Philippine Navy.

LA MONJA - Also known as "The Nun," La Monja is another tiny islet 3.6 miles west of Corregidor and about the size of El Fraile. It is located on the North Channel and is about halfway between Corregidor and the Bataan shore. No fortifications were set up on La Monja and it has for years remained in its pristine state.

EL FRAILE - This small islet, also known as Fort Drum, is about 6.5 miles south-southeast from Corregidor and is less than an acre in size. American engineers razed the tiny rock to the water line and a thick concrete casemate was constructed around it to create an impregnable fortress. It was made to look like a concrete battleship thrusting its bow into the China Sea. Two massive 14-inch twin-gun turrets, one above the other, were set up in its front as well as four 6-inch rifles at its rear. A cage mast topped by a searchlight and a caretaker's shack on the stern completed the ship-like effect. The challenging engineering feat of building Fort Drum took from 1909 to 1919. It has been said that the booming salvos from the "concrete battleship" provided more support for the defenders and more trouble for the Japanese attackers than any other installation in the harbor defenses. Although it was constructed to be bomb-proof, it was blown up from within in a daring raid in 1945 by the U.S. Army and recaptured from the Japanese.

CARABAO - This forty-five acre island, only a few hundred yards from the shores of the province of Cavite, is located about 8.2 miles south of Corregidor. Out of its hard rock American engineers blasted and converted it into a fortified island which was later called Fort Frank. The island has shear cliffs rising a hundred feet from the beach, except for one spot on its eastern shore. To fortify it, the engineers had to emplace all of the armament on a narrow north-south ridge running along its top and on a promontory jutting from the west side.