What can I do in Hong Kong with a three hour layover?

On paper it's theoretically possible, in reality -- having flown into, out of and through HK a fair amount -- I doubt it will work unless you're extremely lucky.

Assuming you want to get to your departure gate thirty minutes before take-off then you have 150 minutes of spare time. You might push that to getting to your gate twenty minutes before take off depending on the flight and airline but some airlines will close the gate and not let you get on (other airlines tend to wait for customers for a bit longer, particularly if they know they should be in the airport).

HK is a big airport, so you might spend ten to fifteen minutes just walking to immigration. Depending on the time of day immigration can take thirty minutes or more. Then you have to factor a potential walk to the departure gate as well as another twenty or thirty minutes getting back through immigration into the airport.

If all the gates are close by and immigration is quiet you might manage the back and forth in thirty minutes, but it's unlikely and in my experience you'll be looking at around at around ninety minutes total for immigration both ways, security coming back in and all the walking. Which, on average, leaves you about an hour to try to get somewhere.

Trains run around every ten minutes, and the closest place is Asiaworld-Expo as Rory Alsop says. So the chances are you'd get there and have to turn around and get back on the train to go back to the airport ...

Also, HK immigration may decide to pull you for extra screening -- they often do this with citizens from certain countries travelling on their own, but the fact that you're trying to leave the airport in such a small window may raise a flag on it's own.

Now, if you have a diplomatic passport, an APEC card, the frequent visitor e-card or something else that would let you bypass the immigration queues it might be a different story. Alternatively if you arrive early you might consider trying to get to immigration and looking at the queue, baring in mind the time it'll take you to get back from wherever you're going.

For completeness I'll add that trains to the city are 24 minutes to Hong Kong station in Central about 18 to Kowloon but neither station is really near anything interesting apart from shopping malls -- and even getting out of the stations can be a bit of a trek.

Like I say, it's theoretically doable, if you really want to risk it but I strongly doubt it's worth it (remember you'll have to pay for transport as well). It depends how comfortable you are with the chance of missing your next flight and generally being in a rush for all of the time.

The airport has a food court (Terminal 1, Terminal 2) which has a bunch of Western and Asian chain fast-food places, so you can get some interesting-ish food there. There's are other restaurants scattered about and your normal shopping places.

There are a few things, including an Aviation Discovery Center, outside the secure zone. I've never been but if you really don't want to sit around air-side it might be worth trying that.

I can only think of two that would be easy to get to:

• Citygate Outlets is about 25 minutes away by bus - a wide range of shops, restaurants etc. On that route there is also the Ancient Kiln Park and Hkia Hostorical Garden.
• Asiaworld-Expo centre is less than 10 minutes away - check out the link for events that will be on when you are there.

There's a chance you won't even get past the immigration officials. A friend of mine had a 9 hour layover and tried to leave the airport to do a little sightseeing. The immigration agent asked him what hotel he was staying in. My friend (a U.S. citizen) said he didn't have one and he was just leaving to sightsee for a few hours. He wasn't allowed past immigration.

Even if you did get past immigration, 3 hours isn't enough time. I've been to Hong Kong a few times and the traffic, taxi queues and distances to anything worthwhile makes it undoable.

There are places within 30 minutes, but what you have in mind is generally a bad idea.

Do the math, 30 min + 30 min return to the city center. That leaves 2 hours, but you should be careful, and plan a longer journey back, in case you don`t find it right away, or there are traffic jams and the like. Add 30 min to the journey.

That leaves 90 min, when you could do something, however, in my experience, you'll be a lot of stress for just walking into a place looking at something and checking the clock each 5 min to get back.

The only trip I'd recommend is the AsiaWorld-Expo, which is just 1 min away from the airport. However, it might be interesting only depending on the exhibitions and events of the day you go there.

Alternatively, you could just hang around the airport, take pictures, have a meal, go to a newspaper stand and the like. That's not all too much time.