verb to be is used in
the meaning of a location the right translation is estar.
Even if it doesn't sound too good but still - if you
can substitute the verb to
be with to be located
then it is definitely estar!
He is in
He islocated in the garden. = Está en el jardín.
London is located in England. = London está en Inglaterra.
are in the mountains.
The goats are located in the mountains. = Las
cabras están en las montañas