Catholics, Protestants, Orthodox, Jews, and other more rare religions are all represented in Vilnius. Indeed, Jews were once the city's largest ethnic group. The most impressive place of worship is the Vilnius Cathedral and its bell tower, but the rebuilt Royal Palace of Lithuania is also worth a stop. Vilnius is one of the only European cities that allow hot air balloons directly over the city center, making for a perfect way to get another perspective on the impressive Old Town. On the other side of the river is the artsy Uzupis neighborhood, a tongue-in-cheek self-declared republic with its own constitution, with articles like, "Everyone has the right to be in doubt, but this is not an obligation."