These twice-baked, ring-shaped bread about five to six inches in diameter go by many different names (friselle, frise, friseddhre, or rusks) and they somewhat resemble dried, hardened bagel halves, but they are a regional specialty from the south of Italy (Puglia, to be precise, and the Salento area of the Puglia region, to be even more precise) and can be difficult to find in other regions of Italy, as well as in the U.S., although I have found them in Italian import stores in Boston's North End (you can also try making your own at home). They are usually made with whole-grain barley and durum flour.
They are also a traditional food in Crete and on other Greek islands, where they are served topped with capers, chopped tomatoes, olive oil, thinly sliced red onions, crumbled feta cheese, and oregano. I suspect that friselle even came to Puglia via Greece, as the area was once colonized by the Ancient Greeks (some small villages exist in Puglia where people still speak an ancient dialect of Greek). In fact, according to The Oxford Companion to Italian Food, local legends in Puglia say that the Trojan hero Aeneas brought them over to Italy; since they keep for a long time, they make good provisions for long sea voyages.
Friseddhre (as they're known in local Pugliese dialect) must be first soaked in cold water for approximately 30-60 seconds to soften, and then they are squeezed or pressed slightly to drain out excess water, drizzled with extra-virgin olive oil and served topped with diced tomatoes, capers, salt, pepper, and fresh oregano. I also will usually rub half of a clove of raw garlic on the frisella before soaking it. They may not sound very exciting, but they’re quite tasty and wholesome, not to mention refreshing in very hot weather, and a great no-cook snack or light meal. They should be soaked only briefly so that some crunch remains. Think of them as a sort of a larger, softer, and more rustic version of bruschetta, or an Apulian version of panzanella, the Tuscan salad made with hard, leftover bread.
If you can't find friselle, in fact, you can easily use the same combination of toppings on toasted slices of bread -- bruschetta, in other words.
If you can find them, salt-packed capers from the Aeolian Islands in Sicily are well worth the extra effort and cost (ironically, in Italy the salt-packed capers are cheaper and it’s harder to find them in vinegar!). The texture is better -- firm and slightly crisp, rather than soggy -- and the delicate flavor of the capers shines through. To use them, you just need to rinse them well, then soak them in some cold water for about 20 minutes to half an hour, then rinse and drain again.