We bought a 3 day travel card for about 3500 huf. This allowed unlimited travel on trams, buses, metro and the river buses. We picked up our river bus at the Margit Bridge after getting the no. 6 tram. The bus then went up the river for about 40 minutes. It then turned round and came back into Budapest. The weather was great and we sat at the front on the top deck and the whole experience was very enjoyable. Tremendous photo opportunities came when going past the Parliament Building and Castle Hill. A must do and way cheaper than one of the many tourist boats.