The Torre di Mariano II rises 22 metres above the Piazza Roma and has dominated the centre of Oristano since the 13th century. Built as part of the city's defensive walls, it is the most visible relic of Oristano's medieval past as the capital of the independent Arborean kingdom — a kingdom that, unlike much of Sardinia, held out against Aragonese conquest well into the 15th century.
The tower's base opens directly onto the square, and on summer evenings the whole of Oristano seems to gather in its shadow. You can't climb it, but you don't need to — it's the backdrop that matters, and it frames the piazza beautifully.