Complex sentence: Within its boundaries it contains a large lake, Kissena Lake, surrounded by playgrounds; a track for speed bicycling; and a number of soccer fields, tennis courts, and baseball fields.
Split into simpler sentences: Within its boundaries it contains a large lake, Kissena Lake, surrounded by playgrounds. In addition to the playgrounds, there is a track for speed bicycling, as well as a number of soccer fields, tennis courts, and baseball fields.