Overview
Nepal is a country truly crushed by poverty, and Kathmandu is its capital, chaos incarnate. The houses, roads, streets — the entire environment outside of tourist areas looks like something from the early 1900s. Besides the ultra-wealthy, the only people with money in their pockets seem to be tourists, and they generally don't leave their purpose-built hotels and restaurants except to sightsee. Seeing that the local population has no access to these hotels and restaurants is genuinely heartbreaking. The only place we saw any locals dining was at the Hard Rock Cafe, and they were most likely from the ultra-rich crowd. I'd never seen anything like this in any country I've visited before. If you're sensitive to these things, a Kathmandu visit might make you more unhappy than happy.
Getting There
The airport is absolute chaos. If possible, fill out your visa form online beforehand and bring a printed copy. If you try to do it at the kiosks there and hit a busy hour, getting out could take hours. No bribery at passport control like in Thailand, which is a plus, they're just painfully slow. For your return flight, arrive at least 3 hours early.
Where to Stay
Our tour booked the Aloft Kathmandu Thamel, a hotel that feels like it doesn't belong to Nepal. Apart from the ventilation issues in the restaurant section and insufficient elevators, no complaints. If your budget allows, it's definitely recommended.
What to See
The city is genuinely rewarding for sightseeing. Among the Durbar Squares we visited, the one in central Kathmandu was the most run-down. That's also where the pushiest street vendors are, be careful. If you make eye contact, getting away without buying something is practically impossible. Patan and Bhaktapur were much cleaner and more orderly than central Kathmandu. If time is limited, these are far better choices than the central Durbar Square.
The Thamel district, despite looking chaotic and old, is surprisingly safe. Great spot for shopping. It's still one of the rare countries where you can find bargains compared to the Turkish lira.
One place I especially want to highlight: a shop called Beni (right in front of North Field Cafe) makes gorgeous gift items from recycled materials, all produced by young Nepali women who are paid above-average wages. It's entirely volunteer-run with zero profit motive. They use their earnings to buy reusable menstrual pads and distribute them to young Nepali girls. In a country with this much deprivation, the effort and contribution is incredible. If you have time, please contribute what you can. The shop owner's husband is an elderly Norwegian gentleman, if you catch him there, you can chat at length. A truly lovely person; you can't help but respect what they're doing.
We had purchased the Everest flight but unfortunately weather conditions cancelled all flights, and we got a partial refund. The day we went to Nagarkot was also very rainy, so we couldn't see the Himalayas at all. I strongly advise against booking the flight or going to Nagarkot on any day that looks overcast. If possible, check the forecast and schedule these for days when the sky is 100% clear.
Among the popular tourist sites, Boudha Stupa and Swayambhunath are architecturally truly unique structures specific to this region. Definitely worth seeing. Beyond those, the two places that impressed us most were, first, Pashupatinath. The cremation ceremonies are something completely different. If you visit in the late afternoon toward sunset, the experience becomes much more mystical. After dark, the atmosphere transforms entirely. We went at this hour by pure luck, and it was one of the main reasons we were so moved.
Second, a much less talked-about area that I think absolutely must be visited: Pharping. The Seshnarayan Mandir temple and the Neydo Tashi Choling Monastery there were incredible. At the second monastery, we got to watch a Buddhist ceremony and it was extraordinary. I'd recommend this as an activity to anyone interested. Do whatever it takes to see it.
The Kirtipur area wasn't bad either, but it's not a must-see. If you have a free day, it's worth visiting for a different neighborhood perspective. Apparently it has the longest suspension bridge in Asia, that was the most noteworthy part.
Finally, one thing I learned: apparently most people who climb Everest bring along Nepali individuals called Sherpas to help carry the heavy equipment. So while Westerners make this grand ascent, the poor Nepalis beside them are doing the same climb to a certain point while also carrying the gear and serving as guides. The real work is done by the Nepalis while the Westerners take the credit.
Overall, Kathmandu is a chaotic city that truly broadens your horizons, but unless you're planning an Everest climb, there isn't much reason to visit more than once.