Twin Island, at , is wooded with exposed bedrock with glacial grooves. The East and West Twin Islands (or the "Twins") were once true islands in Pelham Bay but are now connected to each other and to Orchard Beach and nearby Rodman's Neck by a landfill created in 1937. East Twin Island, a rocky formation with "ribbons of color" caused by sedimentary erosion, is connected to neighboring Two Trees Island via a thin mudflat land bridge. Two Trees Island itself consists of a rocky plateau upon which one can see Orchard Beach and the environmental center. West Twin Island was at one time connected to neighboring Hunter Island via a man-made stone bridge, which now lies in ruins in one of the city's last remaining salt marshes.