Erik had a project in World Religions class to build a replica of any type of place of worship. We found a 3D puzzle, which I think the teacher may count as somewhat less as he didn't build it completely from scratch as most other kids did with theirs.
Fortunately for us, this was a used puzzle and the previous owner separated major sections, so we didn't have one giant mess to start with.
The finished product took us much less time than the original builders. From tear down of the original church to the finish of the dome took over 120 years. An interesting note is that with the shift from Greek cross to Latin cross, visitors cannot see the impressive dome when approaching the Basilica. Only when one is farther away and looking back and down can one see the dome. The obolisk in the plaza is nearly 4000 years old and was brought to Rome from Egypt in 67 BC. Nero brought it to this spot (then called a Circus) where he put to death many Christians, most notably the Apostle Peter, whose remains are interred somewhere beneath the church (there are a number of Popes, two other apostles and a necropolis beneath as well).
Let's see...Vatican City, we'll put that on the list of places to see - eventually.