Complex sentence: Since 1966, the station has also been connected to Milano Porta Garibaldi through a newly built tunnel that has its portal to the south of Mirabello near Piazza Carbonari (the so-called "Passantino").
Split into simpler sentences: Since 1966, the station has also been connected to Milano Porta Garibaldi through a newly built tunnel. The tunnel portal is to the south of Mirabello, near Piazza Carbonari (the so-called "Passantino").