The hook
A single valley holding three former royal cities and some of the holiest sites in Hinduism and Buddhism, a dense concentration of pagoda temples, palace squares, and pilgrim life, much of it rebuilt after a major earthquake.
01Why it's worth it
The Kathmandu Valley was for centuries a cluster of rival kingdoms, and each left a royal palace square, so within a short distance you have three Durbar Squares, Kathmandu, Patan, and Bhaktapur, packed with intricately carved wooden temples and palaces built by Newar craftsmen. Add the two great pilgrimage sites, the giant white dome and watchful eyes of the Buddhist stupa at Boudhanath, ringed by Tibetan monasteries and pilgrims, and the Hindu temple and cremation ghats of Pashupatinath on the river, and the valley is one of the richest sacred landscapes in Asia. A devastating earthquake in 2015 damaged many monuments, and reconstruction is ongoing, which is part of the story now. It is chaotic, polluted, and intense, and also extraordinary.
02How to experience it
Give each of the three old cities its due; Bhaktapur and Patan are calmer and better preserved than central Kathmandu. Join the circuit of pilgrims around Boudhanath at dusk, and see Pashupatinath respectfully. Use the valley as the cultural bookend to any trek in the mountains beyond.
The honest note
Kathmandu splits opinion in the r/solotravel Nepal thread more sharply than anywhere else in the country, and both sides are worth carrying.
The complaint is specific and comes from a trekker comparing it to the mountains: "the Sherpa people are kind, quiet, reserved. Kathmandu seemed more like India, where everyone is trying to rip you off. The tour guides take you to various shops with high-pressure sales, and their attitude is 'oh, it's your choice to buy from this overpriced high-pressure stop.'" Book activities through your guesthouse rather than a street agent, and treat any unrequested detour into a shop as the transaction it is.
The enthusiasm is just as specific, and about something no guidebook leads with: "the rock and roll scene in Kathmandu is AWESOME — best experience at a live show I've ever had, with a mix between local Nepali rock and modern western rock." They name Purple Haze on Paryatan Marg.
One structural tip from a two-month itinerary in the same thread: most people rush the valley to get to the trailhead, but Bhaktapur is worth several days of its own, and Nagarkot on the rim gives the Himalayan skyline without a trek.