I'm an American living in Viterbo for two years--as part of a program that has been here for a decade--and for the Americans we have met, Monastero is the top pick for an inexpensive dinner out to have excellent pizza at an amazing value. We go often, as do our friends living here.
We almost always share one of the enormous double pizzas (with different orders for the different halves) and it is a full meal for only 15 euro a couple, plus some cheap beer or wine. The choices for pizza toppings are dazzling.
In summers, you can eat outside on the large, covered piazza next to a stone pulpit from which St. Thomas Aquinas preached in the middle ages. It's a charming location. This is a very very popular spot for Viterbese, so us Americans tend to show up early. Get there at 8:00 and you will wait; get there at 7:30, and you get a seat.
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