The Tibidabo is Barcelona's highest view mountain with a church on the highest point and under this an amusement park with many nice attractions with attractions for the whole family (also for the little childs).
Special characteristics: Very beautiful view over Barcelona and the sea.

Car: There is an "exit" from the Ronda de Dalt (detour ring) on the Tibidabo.
Bus: The Tibi bus leaves from the Plaza Catalunya.

You find further information in English/Spanish on this site.