Bolsena is a town and comune of Italy, in the province of Viterbo in northern Lazio on the eastern shore of Lake Bolsena. It is 10Â km (6Â mi) north-north west of Montefiascone and 36Â km (22Â mi) north-west of Viterbo. The ancient Via Cassia, today's highway SR143, follows the lakeshore for some distance, passing through Bolsena. Bolsena is named "the city of the Eucharistic miracle" from which the solemnity of Corpus Domini had been extended to the whole Catholic Church.