Ostia is a large neighborhood in the X Municipio of the municipality of Rome. Ostia (also called Ostia Lido or Lido di Roma or Lido di Ostia) is also the only municipality or district of Rome on the Tyrrhenian Sea and many Romans spend their summer holidays here. With about 85,000 inhabitants, Ostia is the first or second most populated fraction of Italy, depending on whether you include Mestre.