You have to book ahead online, but it’s worth it to peek inside the grandiose President’s House. Formerly home to the British Viceroy, it has 340 rooms, with 2.5km of corridors. However, visits are limited to the domed Durbar Hall, the presidential library, and the gilded Ashoka Hall.
You’ll have to leave cameras and phones at the entrance, but there’s a chance to take pictures close up of the outside before/after your visit.
