the United States Census Bureau, the city has an area of , of which is land and (10.90%) is covered by water. Lakeland is within the Central Florida Highlands area of the Atlantic coastal plain, with a terrain consisting of flatland interspersed with gently rolling hills. Lakes The dominant feature in Lakeland is the city's many lakes. Thirty-eight lakes are named, with a number of other bodies of water unnamed, mostly phosphate mine pits that eventually filled with water. The largest of these is Lake Parker, which is in size. Much of the culture of Lakeland revolves around its many lakes, and many people use the lakes as reference points in much the same way people in other towns use streets as reference points, such as "I live near Lake Beulah." In addition to Lake Parker, some of the more prominent lakes in the Lakeland area are Lake Hollingsworth, Lake Morton, Lake Mirror, and Lake Gibson. Swans are one of the most visible features on the lakes near downtown Lakeland. They have a long history, the first swans appearing around 1923. By 1954, the swans were gone, eradicated by alligators and pets. A Lakeland resident who mourned the passing of the swans wrote to Queen Elizabeth. The royal family allowed the capture of two of the royal swans, and the swans now on the lakes of Lakeland are the descendants of the one surviving royal swan sent by the Queen. In July 2006, Scott Lake, one of the city's lakes, was almost totally drained by a cluster of sinkholes. Later the lake partially refilled. Climate Lakeland, like most other parts of Florida north of Lake Okeechobee, is in the humid subtropical zone (Köppen climate classification: Cfa). Typically, summers are hot and humid with high temperatures seldom dropping below 90 °F and 70 °F for the overnight low. Like most of Central Florida, afternoon thunderstorms are the norm throughout the summer. Winters in Lakeland are drier and warm, with frequent sunny skies. High temperatures range in the mid 70s during the day, with lows in the 50s. Cold snaps drop temperatures below freezing twice a year on average. Demographics As of 2010, 48,218 households were in the city, with 15.5% being vacant. As of 2000, 23.5% had children under the age of 18 living with them, 43.5% were married couples living together, 13.7% had a female householder with no husband present,