Wiesbaden has long been famous for its thermal springs and spa. Use of the thermal springs was first documented by the Romans. The business of spring bathing became important for Wiesbaden near the end of the Middle Ages.

By 1370, sixteen bath houses were in operation. By 1800, the city had 2,239 inhabitants and twenty-three bath houses. By 1900, Wiesbaden, with a population of 86,100, hosted 126,000 visitors annually. Famous visitors to the springs included Johann Wolfgang von Goethe, Fyodor Dostoevsky, Richard Wagner, and Johannes Brahms. In those years there were more millionaires living in Wiesbaden than in any other city in Germany.

Gambling followed bathing en suite and in the 19th century Wiesbaden was famous for both. Its casino ("Spielbank") rivalled those of Bad Homburg,

Baden-Baden and Monaco. In 1872, the Prussian-dominated Imperial government closed down all German gambling houses. The Wiesbaden casino was reopened in 1949.

The Schlossplatz ("palace square") is situated in the center of the city, surrounded by several outstanding buildings. The ducal palace was begun under William, Duke of Nassau. Its foundations were laid in 1837 and it was completed in November 1841 (two years after William's death). For the twenty-six remaining years of ducal authority it was the residence of the ruling family. It later served as a secondary residence for the King of Prussia 1866 to 1918. It was later used as a headquarters for French and British occupying forces after World War I, then as a museum. Since 1945, the building has served as Landtag (parliamentary building) for the federal state of Hesse. The site of the palace had been that of a castle, probably from the early Middle Ages, around which the city had developed. While nothing is known of the former castle, remains of it were uncovered during excavations after World War II. The new town hall was built in 1887. Engraved in the paving in front of the town hall are the heraldic eagle of the Holy Roman Empire, the lion of Nassau, and the fleur-de-lis of Wiesbaden. The old town hall, built in 1610, is the oldest preserved building in the city center and now is used as a civil registry office. The Protestant Marktkirche ("market church") was built from 1852 to 1862 in a neo-Gothic style. Its western steeple is 92 m (302 ft) in height, making the church the highest building in the city.

Kurhaus with Fontain of the Bowling Green

The monumental Neo-Classical Kurhaus ("spa house") was built at the request of Kaiser Wilhelm II between 1904 and 1907. Its famous Spielbank (casino) is again in operation. In front of the Kurhaus is a lawn known as the Bowling Green. To one side of the Bowling Green is the Kurhaus Kolonnade. Built in 1827, the 129 meter structure is the longest hall in Europe supported by pillars. To the other side is the Theater Kolonnade, built in 1839. It is adjacent to the Hessian State Theater, built between 1892 and 1894.

St. Bonifatius, the first church for the Catholic community after the Reformation, was built from 1845 until 1849 by Philipp Hoffmann in Gothic Revival style and dedicated to Saint Boniface.

The Russian Orthodox Church of Saint Elizabeth was built on the Neroberg from 1847 to 1855 by Duke Adolf of Nassau on the occasion of the early death of his wife Elizabeth Mikhailovna, who died in childbirth. The architect was Philipp Hoffmann.

Another building from the regency of Duke Wilhelm is the Luisenplatz, a square named for the Duke's first wife. It is surrounded by Neoclassicist buildings, and in the middle of the square is the Waterloo Obelisk, commemorating the Nassauers who died in the wars against Napoleon. Apart from the palace in the center, the ducal family had a large palace on the banks of the Rhine, known as Schloss Biebrich. This baroque building was erected in the first half of the 18th century.

North of the city is the Neroberg. From the top of this hill it is possible to view a panorama of the city. The Nerobergbahn funicular railway connects the city with the hill.

One of the three Hessian state museums, Museum Wiesbaden is located in Wiesbaden.