Kathmandu is a base camp to all trips in Nepal from abroad. Here are couple of from zillion tips what to see there.
Thamel: a tourist neighbourhood with lots of budget hotels, restaurants, shops and opportunities to photograph
Swayambhu monkey temple high up above 365 steep with great views
Patan Durbar square: UNESCO World Heritage from 3rd century. Being reconstructed after severe damag by 2015's earthquake.
Bouda: one of the world's largest Buddhist stupas
Pashupatinath: oldest Hindu temple complex in Nepal where hindu funerals take place
Click to photos you like to navigate there.