The green dome was built by one of the Uthmani Caliphs. The second door from the right (obscured) is Jibreel Gate, which is the sunnah gate to enter the masjid. Its not all easy to enter by this gate though, you’ll have to enquire what times its open to stand a proper chance. The gate on the left, is al-Baqi gate, but is actually an exit gate. Underneath the dome is the area of the Prophets (pbuh) rawdah.
