Brown cliffs rise from the floor of the Paglia Valley to the high volcanic plateau on which the city sits. Surrounding this spectacular sight are the vineyard-covered hills which produce the well-known crisp white wine by the same name. The most impressive monument of the city is without question its Duomo, begun in 1290, a masterful blend of Romanesque and Gothic styles designed by the Sienese architect Lorenzo Maitani. Luca Signorelli’s outstanding frescoes of the Apocalypse, painted between 1497 and 1504, have been restored and can now be seen in the chapel to the right of the main altar. Alongside public gardens surrounding the ruins of an Etruscan temple is the Pozzo di San Patrizio, a well dug in 1527. The shaft is 63 m deep and is lined with an ingenious double helix staircase which enabled packhorses to descend to collect water and return by a separate staircase. The idea is said to have come from Leonardo da Vinci. Pope Clement VII commissioned Antonio da Sangallo to ensure that Orvieto would always have a water supply.