The Cittadella: The golden limestone ramparts of the Cittadella dominate Rabat/Victoria, Gozo’s tiny capital and its hilltop site has been occupied for more than three thousand years since first fortified by the early Bronze Age inhabitants of the island.
The Ggantija temples: The Ggantija temples (the word Ggant meaning giant in Maltese) are the oldest free standing stone structures in the world, predating Stonehenge by an estimated 1,000 years.
Dwejra & the Azure Window: This extraordinary natural arch – standing some fifty metres above the crystal clear sea in the protected area of Dwejra – is an iconic site in Gozo and has been used as a location in many recent major feature films.
Scuba diving: Gozo has some of the best diving in the entire Mediterranean with excellent visibility often in excess of 40 metres, a wide variety of dive spots for all levels of experience, and easy access from beaches and inlets around the island.
Victoria / Rabat: Gozo’s capital, still known as Rabat by Gozitans despite being renamed Victoria in 1887 for the queen’s golden jubilee, lies on the southern side of the imposing medieval Cittadella and is a pleasant small town of narrow streets and sunlit squares.
Source: http://www.responsibletravel.com/holidays/gozo/travel-guide/things-to-see-do-in-gozo