If you're in Hong Kong and you can take two days (or more) off, then travel agents on Nathan Road (Kowloon) can arrange a trip to Beijing (flights, hotel and visa) with 24 hours' notice. It's not so expensive and well worth the effort. Just one or two nights in Beijing are very rewarding.
Bottom of Nathan Road (ferry end) on Kowloon. There are many travel agents.
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