Estab­lished in the year 301, the sole remain­ing Ital­ian city state is also the world’s old­est sur­viv­ing repub­lic. While the three his­toric tow­ers that adorn the San Mari­no flag are now large­ly orna­men­tal, they still keep watch over the moun­tain­ous coun­try­side. For views that stretch from bor­der to bor­der, climb to the pic­turesque Roc­ca Guai­ta, an 11th-cen­­tu­ry tow­er that for­ti­fies an already-for­bid­d­ing sum­mit – over the cen­turies it’s helped fend off invaders, housed the nation­al guard and even served as a prison.