The Neptunalia was the festival of Neptune on July 23, at the height of summer. The date and the construction of tree-branch shelterssuggest a primitive role for Neptune as god of water sources in the summer's drought and heat. The most ancient Roman calendar set the feriae of Neptunus on July 23, two days after the Lucaria of July 19 and 21 and two days before the Furrinalia of July 25. This holiday as an obscure archaic two-day festival in honour of Neptune as god of waters, celebrated at Rome in the heat and drought of the Roman summer. (Varro, De lingua Latina vi.19). It was one of the dies comitiales, when committees of citizens could vote on civil or criminal matters. In the ancient calendar this day is marked as Nept. ludi et feriae, or Nept. ludi, from which Leonhard Schmitz (in Smith, see link) concluded that the festival was celebrated with games (ludi). Respecting the ceremonies of this festival nothing is known, except that the people used to build huts of branches and foliage (umbrae, according to Festus, under " Umbrae"), in which they probably feasted, drank, and amused themselves (Horace Carmina iii.28.1, &c.; Tertullian De Spectaculis ("On Celebrations") 6). Compare to the "booths" under which Jews celebrate Sukkot. Festivals in honor of Neptune are still very much alive today. The Festival Of Neptune in Virginia Beach celebrates it’s 40th anniversary this year.