Prague has an excellent network of metros, trams and buses, and all for free if you've reached 70. No special card to obtain, just show your passport if you ever happen to be questioned. Even if you aren't that old, fares are very inexpensive, with quite a few options like single tickets and passes of various lengths. The system is completely integrated, so a ticket works on all modes. I didn't experience them, but there are also funiculars and ferries included in the system.

From the airport there is are a couple bus lines that connect to different points on the metro lines, and then the metros will get you at least very close to most anywhere in the city. I think this is the first time I've ever gotten from a foreign airport to a downtown hotel for free.

The metros run very frequently - between 3 and 10 minutes apart depending on time of day, and the trams and buses are also frequent. The metro has three different lines, and together they are over 40 miles long.

All the lines I rode were clean, comfortable and well marked. Signage and announcements often also in English. At the end of one metro line is a really lovely shopping mall, and a short walk beyond that is an IKEA.

The routes are useful for tourists, with stops by Prague Castle, the Beer Museum, a Chocolate Museum and many other tourist attraction destinations.