It's a rainy day here in Kathmandu, and unfortunately, there aren't a lot of sites to see indoors. In the West, Romans invented the concept of interior space. Before them, lives were largely lived out-of-doors with small shelters just for sleeping. You can see the difference by comparing a Greek temple with a Roman basilica (which were often converted pagan temples). The Greeks expected the people to stand outside, with only priests and some statues sheltered by a roof.
Here, that Roman innovation never caught on in religious architecture. There is very little room inside of pagodas and temples, and Buddhist stupas have no interior at all. That is my long-winded way of saying the interesting things to see here aren't terribly fun on a rainy day.