The Pods can be accessed through the Ae'gura library - there are 4 of them.

The following link is a very good resource for knowing when to catch the gateways inside.
http://www.uru-reallife.com/dnidatetime/release6/map.html

Some tips:
1.) Your computer's clock affects when the gates appear inside the pods (the gateway is a glowing symbol). The website above will give you the calculated time for when the gateway appears.
2.) I always recommend being there at least 10-20 minutes beforehand, and stand near where the gateway appears. Turn your sound up, you will hear a sound effect when it appears and disappears.
3.) I've been doing research on the Pods after I missed two gateways in a row. I've discovered that the website can be off anywhere from 45 seconds to at least 3-4 minutes. So when it gets close to the time for the gateway to appear - just focus on the game.
4.) Research also tells me that when the gateway first is triggered by your time, it can take up to 20 seconds to fully appear. You will then have 30 seconds to walk through it. If you do not walk through it before it disappears, you will have to wait for the next cycle.
5.) Sometimes visual effects/bugs can occur. For instance, today Payiferen's gateway didn't fully disappear. I was timing how long it was open and it partly disappeared. I was able to walk through it without being transported. If your gateway never appears, don't worry - just catch it the next time you can.

I hope this helps. The biggest thing for me was the 30 seconds to walk though the gates - it can be very easy to miss the gates if you step out for just 30 seconds to a minute.

The Pod portals not disappearing after closing is a feature, and not a glitch. Check out each portal after they vanish! Some are different from others!

curious, why do you say not a glitch? What I've seen in the python code and myself, out of 10 times or so, all closed except one. Therefore you've sparked my curiousity.

Spoiler tags are not necessary in the Spoilers, Hints and Tips section.