Zenkō-ji善光寺
A temple that belongs to no single school: Tendai and Jōdo priests run it together, and by tradition it was founded in 644. The main hall (1707) is a National Treasure. The grounds cost nothing; the inner sanctuary and the Okaidan, a pitch-dark corridor under the altar, take a ¥800 ticket (¥1,500 for the set with the Sanmon gate, the sutra library and the museum). From December to February the inner sanctuary closes at 16:00.
Allow 1h 30m to 2h with the Okaidan and the Sanmon. Parking is in coin car parks around the gate (fees not checked). The Zenkō-ji guide has the dawn service and the ticket detail.