Which country's flag features a white cross on red?

Switzerland, and it is one of only two square national flags - Vatican City is the other. The square shape is oddly consequential: the Swiss flag flown at the United Nations had to be made rectangular to match the others, which required a specific decision.

The Red Cross emblem is the Swiss flag with the colours reversed, chosen in 1863 in honour of Henry Dunant, a Genevan who had witnessed the aftermath of the battle of Solferino - 40,000 casualties left largely untended - and campaigned for a neutral body to care for the wounded of any side. He won the first Nobel Peace Prize and died in a hospice, having gone bankrupt and spent years forgotten.

The cross itself is much older, appearing on the banners of the Old Swiss Confederacy from the fourteenth century as a field sign so that troops from different cantons could recognise each other. Switzerland has no single founding language or ethnicity - four official languages and cantons that were independent states - so the flag is doing unusually heavy lifting as the thing everyone shares.