The Castle of Frascarolo is reached by a turning off the road that connects Induno Olona and Valganna. Up until the construction of the tunnel at Grotte di Valganna, a project dating to the end of the last century, the person who wanted to travel between Varese and Ponte Tresa had to take two roads which, in any case, led to the Abbey of San Gemolo in Ganna.
The first one passed through La Rasa and Brinzio and was 'guarded' by the so-called tower degli Ariani placed at Santa Maria del Monte. The second followed Valganna although in being unable to pass through the narrow neck of the banks the road climbed up to Frascarolo to then - probably - descend to the Valganna Plain, roughly where today one has the locality called Antro of the same tunnel, a little later meeting with the road from Arcisate by way of the Passo del Vescovo [Bishop's Pass].
The castle which stood along this road probably had origins sunk in the early Middle Ages although we only have documented news of it starting from 1160.
Certainly controlled by the Abbey of Ganna during the XIII century, it suffered the same destiny, passing into the hands of the commendators who followed the one after another in the management of the Abbey's possessions starting from the XV century. In 1543 the castle became the property of Gian Battista Medici, Marquis of Marignano, the brother of Gian Angelo (later Pope Pious IV) and Gian Giacomo - called the Medeghino in whose service we find the congenial engineer Agostino Ramelli, who was probably born in Ponte Tresa.
Since then - with the exception of brief periods - the castle remained the property of the Medici family.
Legend has it that Carlo Borromeo, future Archbishop of Milan, sojourned there.
The present-day appearance of the Castle has been strongly influenced by the transformations which the Medicis carried out during the XVI century in order to adapt the building to the demands of sixteenth-century aristocratic life. During this period it lost its defensive physiognomy (the imposing western tower still remains as testimony of its original purpose).
The Castle cannot be visited.
With a mountain bike it is possible to continue beyond the Castle and descend to the Valganna, first by following the carriageroad to the Cascina Montallegro and then the paths through the woods. In this way one is covering the zone of the old road. From Valganna a bridle-path climbs its way up to the Passo del Vescovo, also able to be reached by a path that keeps itself half-way up on the mountain.
From the Pass - the old alternative road to the Frascarolo crossing and road of communication between the parish of Arcisate and the Abbey of Ganna - one descends into Val Ceresio. From here it is possible to easily return to Induno Olona.