You notice a beautifully carved marble altar outside the Temple of Isis, with the inscription ISIDI SACR[um], "sacred to Isis." On the front is carved a woven basket called the cista mystica, used to hold snakes for rituals in mystery religions such as the rites of Dionysus and the cult of Isis. The basket on this altar has a relief of the sacred boat of Isis, part of an important festival held on March 5 called the navigium Isidis, when Isis grants her blessing to the opening of the season for sailing on the Mediterranean. This fresco from Pompeii shows the boat of Isis between two busts of the river Nile; in the foreground is the cista mystica flanked by two snakes, Agathodaemon (sacred to Serapis) and Uraeus (sacred to Isis). On the right side of the altar is a relief of Anubis, jackal-headed Egyptian god associated with mummification and the afterlife.