Surprisingly there are 3 churches all called Santa Maria in Piazza del Popolo. Confusion is inevitable. Even a few of the photos attached to reviews below show the wrong church.
The easiest way to spot it is to stand in the middle of the piazza, walk towards the large gateway, and the white facade of the church will be on your right.
The other difficulty in visiting this church is that it’s closed for a big chunk of time in the middle of the day. On weekdays, it closes between 12 - 4pm (weekends are a little different).
I should’ve checked before visiting but didn’t. As a result I missed out which is really disappointing because everything you want to see here is on the inside.
The facade is rather plain. Certainly its not exceptional. However inside are paintings by Raphael and Carravaggio and works by the Baroque genius, Bernini, who was so in demand that he received commissions from 8 different popes.
Note: The website says that it’s currently temporarily closed to all visitors and is undergoing restoration work. It will re-open November 2024. Perhaps the hours may change after this date but its definitely worth checking before visiting.