A rare event occurs in Alviano; in fact, here a barrage of the Tiber River has produced over 500 hectares of marsh, lake, swamps, hygrophilous wood, and originated an important food supply station for nearly 150 species of aquatic birds, including the most rare ones as cranes, wild gooses and ospreys. The oasis has been suitably conceived for the protection and enhancement of these species. The entrance to the protected area is located in Madonna del Porto, in the municipality of Guardea, where two paths begin (4 km in total); they are equipped with hides, towers, footways and open-air classrooms at the heart of the swamp, from which it is possible to become part of unforgettable charm.

This area is protected by the environmental association of WWF, whose operators are committed in ensuring its best use. This type of reality is a very interesting example of management, since it derives from an agreement between WWF and local authorities. In the territory of Alviano, in the open countryside, it is possible to visit the Villa of Popigliano dating back to the last decades of the 1st century b.C.. Several Romans built their villas between Orte and Orvieto, along the Tiber River. The excavations carried out from 1977 to 1981 brought to light the villa only partly, but it is however possible to see some of its fundamental aspects as the structure made up in opus reticolatum (a Roman building technique), developed around an atrium, where rainwater falling from an opening in the ceiling (compluvium) was collected in the impluvium (a quadrangular basin embedded in the floor). Around it, a portico allowed the access to the rooms of the villa and, at the rear, before the main entrance, there was the most sacred room, the “tablinum”, where the family used to meet and where guests were received. Next to it there was the dining room and from here it was possible to go to the garden (hortus), surrounded by columns. The villa had very few windows, as a typical Roman villa.

The excavation campaigns have unearthed a huge quantity of remains, among which are the floor in cement pavement and opus spicatum, although partly destroyed by the works, a travertine stair that suggests the existence of floors on different levels, the walls surrounding two communicating rooms, one of which is covered by plaster, the fragments of black-painted ceramic and the Italian sigillata, whose use is documented by some amphorae, glasses, and a bronze as dating back to the Antonine period.

Traces of collapses and fires show a period of crisis, dating back to the 3rd century AD., when the villa was abandoned, and only a tile grave shows the last occupation of the site, by that time tumbledown.