Although this is the square of Catholicism's most important church (Yes St John Lateran is ranked higher than the more famous St Peter's Basilica), this piazza is surprisingly boring! Immediately in front of the church facade, this piazza is literally a flat concrete surface with some patches of grass. Perhaps this is intentional to focus more on St John Lateran's Baroque facade.
Either way, unlike many beautiful piazzas throughout Rome, this is unfortunately an open space that you must traverse to enter the church, which is a huge contrast to the more dramatic St Peter's Square in the Vatican. Aside from admiring and photographing the church facade, you really have no reason to linger in this piazza. Besides, the church itself has so many things to see inside!
By the way, while this is technically not a part of this exact piazza, you can actually find the world's largest Egyptian obelisk behind the church! This obelisk is said to be so huge that a custom ship had to be built to transport and the ship was sank after its purpose because it was too impractically huge!
---
tl;dr version:
1) Important church's piazza but pretty boring
2) World's largest Egyptian obelisk in the back read more