Dividing the city's Buda and Pest sides is the impressive Danube River. Flowing roughly 1,770 miles from west Germany through Austria, Slovakia, Croatia, Serbia, Bulgaria, Romania, Moldova and, of course, Hungary, before meeting the Black Sea in southern Ukraine, this sprawling river is the second longest in Europe. Along its Budapest shores, travelers will find iconic sights like the Hungarian Parliament and Buda Castle.

Recent visitors highly recommend checking out the Danube River on foot or by boat. If you decide to go for a stroll, consider doing so at the Danube Promenade, which offers picturesque views and the must-see Shoes on the Danube Bank Holocaust memorial, according to past travelers. Many also suggest signing up for an evening sightseeing cruise through local operators like Legenda Sightseeing Boats and Portum Lines.

The Danube River is free to visit 24 hours a day. Several tram and metro lines make stops within walking distance of the river's banks, and a few high-end hotels – including the Budapest Marriott Hotel and Hotel Zenit Budapest Palace – sit close to the promenade. A variety of bars and restaurants are also available by the river's east bank.

Boat excursions generally last about an hour and include a cocktail or nonalcoholic beverage in their rates. Expect to pay 2,790 to 5,500 forints (or about $11 to $21.50) per person, though some companies waive or reduce prices for children. For a list of available boat tours, visit Viator's website.