Assumption Day (celebrating the Assumption of Mary), August 15th, is a nationwide public holiday in several countries including Spain. (Take this into account for your trip!).
Each year, Valencians celebrate this day with a typical procession in honor of Virgin Mary that is also considered one of the oldest in the city, dating back to 1352.
During the day, different Eucharistic acts are held, including veneration to a statue of the Virgin that can only be seen once a year; the current sculpture being honored was carved in 1940 by Vicente Benedito Baró (1884-1956). It’s moved around the city and taken to the Cathedral.