As I recall, Niigata itself wasn't very interesting, but it's the departure point for the ferry to Sado Island, which is pretty interesting from a historical and folkloric point of view. Like everywhere else in Japan, it's touristy, but it's more interesting than Niigata, which I've heard of only in connection with its being a favorite port for Russian sailors, even in the Communist days.

See a guidebook or the JNTO's PDF about Sado for more information.

The big temple in the center of Nagano is called Zenkoji, and yes, it looks like most other temples, but I thought the main street approaching it was one of the most attractive in Japan. Again, the JNTO website probably has a PDF about Nagano.