American Alligators (Alligator mississippiensis Daudin) are ecological engineers who alter the Everglades landscape through creation and maintenance of small ponds, called alligator holes, that play a key ecological role by providing both drier and wetter habitats for other organisms. The objective of this study was to compare morphology, vegetation, and activity of alligators in twenty natural and nine man-made alligator holes in ridge and slough wetlands of the central Everglades. All alligator holes were circular in shape and excavated to flat limestone substrate. Nine natural alligator holes were associated with tree islands and 11 were surrounded by sawgrass marsh. Man-made alligator holes were adjacent to islands constructed as high water refugia for deer. Marsh alligator holes were smaller and shallower than alligator holes associated with tree islands. Alligator hole size was correlated with water depth. Alligator holes surrounded by marsh had less diversified surroundings and lower species richness than alligator holes associated with tree islands. Alligator holes contained species of vegetation not found in the surrounding marsh. Seventy-nine percent of the alligator holes had signs of recent activity by alligators. Larger alligator holes associated with tree islands had adult and hatchling alligators and smaller marsh alligator holes contained juvenile alligators. Understanding the ecological role of alligator holes will be critical to planning and evaluating restoration of the Everglades ecosystem.