I encountered the following two sentences in my Italian Rosetta Stone program:
Vanno a cavallo sulla spiaggia.
Va in bicicletta sulla spiaggia.
However, I can't understand why the former uses
a while the latter uses
in in preposition. Both use
andare and express what to ride in to andare in spiaggia.
Is there any explicit criterion on when to use
a in andare?