Thalamegos was a type of houseboat, yacht, or barge mainly found in the Nile River, Egypt. They were used as freight carriers and ferry. The most famous and largest thalamegos was a huge twin-hulled catamaran, a two-story Nile River palace barge that was commissioned by Hellenistic king Ptolemy IV Philopator for himself and his wife Arsinoe III ca. 200 BCE.