For 10 points, name this city on the Danube, the capital of Hungary.
This city's Roman ruins advertise to tourists that Marcus Aurelius wrote his Meditations here when this city was a Roman settlement called Aquincum. Saint Gerard was martyred by being thrown off of the Gellért Hill in this city, which now houses ritzy houses and the citadel. This city's Castle Hill is served by a funicular railway, which leads up from a famous bridge to the thirteenth-century Royal Palace. This city subsumes three islands, Obuda, Csepel, and Margaret. Its name is a portmanteau of the names of a flat city and a hilly city that merged to form this metropolis; its constituent cities are now connected by the Szechenyi Chain Bridge. For 10 points, name this city on the Danube, the capital of Hungary.
This city's Roman ruins advertise to tourists that Marcus Aurelius wrote his Meditations here when this city was a Roman settlement called Aquincum.
Budapest [prompt on Buda or Pest before “portmanteau”]