There are several cities in Europe with a lot of cobbles streets.

Riding a Brompton on cobbles is not pleasant at all and you need to slow down if they are bad.

Having a front suspension like the Birdy really help.

Using a Frog (ETRTO 305 smaller wheel version of the Birdy) would probably help to have a better bike geometry (with this fork from a ETRTO 355 Birdy, the front of the Brompton is higher than with the factory fork).