The Roman baths featuring a combination of steaming, cleaning, and massage appeared wherever the Romans made conquests. In Rome itself the aqueducts fed sumptuous baths such as those of Caracalla, which covered 28 acres (11 hectares). From the 1st century BC onwards, the Romans built establishments called balneae or, later, thermae incorporating suites of rooms at different temperatures. A typical installation would include a tepidarium (warm room, probably without bath), a caldarium (hot, with plunge bath), a frigidarium (cold, also with bath), and an apodyterium (changing-room). Elaborate examples might also include a laconicum (room with dry heat), a swimming bath, an exercise area (palaestra), gardens, and a library. These complexes were important social meeting-points and were not limited to high society. Most large private houses from the 2nd century BC onwards had their own bath suite. The four large series of baths at Rome were built by Titus, Trajan, Caracalla, and Diocletian. Baths existed as early as the 4th century BC.