The Emirates Air Line is a cable car that allows you to cross the Thames from North Greenwich or the Docklands. On a beautiful day you have a magnificent view of the Docklands, Canary Wharf, London City Airport and the Thames Barrier. You can also, if you look in the direction of North Greenwich and the O2 Arena , see the Old Royal Naval College and the Queen’s House in Maritime Greenwich.
The “flight” takes about 10 minutes is very nice when the weather is good. If the weather is not that good I would not recommend this, because the view is than not as good.
You can buy single tickets or “Boarding Passes”, but you can pay better with your Oyster Card. With Oyster Pay-as-you-go you will get a £1 discount.