In the town of Bomarzo, you can visit probably the most unusual park in Italy - the Park of Monsters (Sacred Forest). History of the park is not known for sure, it is believed that it was built in the XIV century and was at that time called "Villa of Wonders". Until 1954, the park was in ruins, as can be seen at the photo exhibition inside the administration building.
Curiously, one of the first visitors to the park was Salvador Dali in 1938. Some motifs of the park can be seen in his painting The Temptation of St. Anthony (1946).
For details about opening hours and prices, see the official website.
More information about the park is here.
Getting there: Go by train to Orte Scalo or Viterbo, then by bus of the Cotral company to Bomarzo (schedule of the bus from Viterbo and from Orte).