The first Europeans to explore San Diego Bay and its environs were members of the maritime expedition led by Juan Rodríguez Cabrillo in 1542. Sebastián Vizcaíno visited again in 1602, but no settlement was made until the fort was begun in May 1769. On July 16, 1769, Mission San Diego de Alcalá was established by Junípero Serra on Presidio Hill. The presidio had a commanding view of San Diego Bay and the Pacific Ocean, allowing the Spanish to see potential intruders.