Each of the three Marzes has a main highway from Yerevan. One goes to Gyumri, one to Vanadzor-Alaverdi-Georgia, and the third to Dilijan-Noyemberyan-Georgia via Lake Sevan. Options to get out to each of these regions is day trips/tours, renting a car, taking a taxi, or public transportation. Gyumri, Vanadzor and Dilijan are all no more than 1.5-2 hours from Yerevan, and a day trip is easy. If you want to go beyond these cities though, it can become harder to fit it all into a day trip, and looking into spending the night becomes worthwhile.