Public Transportation in Prague

Here's the DPP website: www.dpp.cz

The relevant bit is italicized below:

The group of senior of 60-65 years is always valid from the day of the 60th birthday to the day preceding the 65th birthday, the group of senior of 65-70 years is always valid from the day of the 65th birthday to the day preceding the 70th birthday and the group of senior over 70 years is always valid from the day of the 70th birthday.

*In order to claim free transport for seniors of 65-70 years, it is necessary to present the Document of the entitlement to special prices of fare for a senior of 65-70 years or the paper PID Card Senior 65-70 years.

**In order to claim free transport for seniors over 70 years, it is sufficient to prove age (for example by identity card or by passport). In the PID trains in the area of the Capital City of Prague, it is sufficient to prove age (e.g. by identity card, passport or another officially issued personal document with a photograph, name, surname and date of birth, the PID Card Senior 70+, or an electronic discount application). Free transport is not provided in AE line.

In simple English, just show your passport.

Thank you Marcus!

Reading a bit further, for those aged 60-69 https://pid.cz/en/discounts/#senior

There is a discounted fare for those aged 60-64,
and free riding for those aged 65-69

With either of these documents, issued locally for a fee (not revealed)

A chip card with an appropriate application
A PID pass for Senior from 65 to 70 years

I use the PID card for 60-64 year olds, had it a few years now, cost me 20kc and then I pay 130kc for a monthly pass every time I come into the city, you need ID like your passport and a passport style photo to get the pass and only takes about 5 mintes to set up,I got mine at the airport but there are other places in the city to get them. My BiL got the one for 65-69 year old last year, again 20kc for the card but free travel after that.,Only really worth the effort if you are going to be in the city for more than a few days or going to be travelling on the public transport system a lot.

BTW in the 3 + years I have had the pass and about 100 days in the city since then I have never been asked to show my pass on any form of transport.