We have two competing theories. One is that Israel is making everything up. The other is that Iran is pursuing nuclear weapons. At least the second one seems to have some evidence backing it up like secret underground facilities with centrifuges, enriched material, and yes, that warehouse in Tehran. The theory that Israel is making everything up doesn't seem that well supported.

https://www.bbc.com/news/world-middle-east-50382219 "The International Atomic Energy Agency (IAEA) has found uranium particles at a site in Iran that had not been declared by the Iranian authorities.

A confidential report, seen by the BBC, did not say exactly where the site was. But inspectors are believed to have taken samples from a location in Tehran's Turquzabad district.

That is the area where Israeli Prime Minister Benjamin Netanyahu has alleged Iran had a "secret atomic warehouse". "

https://www.reuters.com/article/world/exclusive-iaea-found-u...

"VIENNA (Reuters) - Samples taken by the U.N. nuclear watchdog at what Israel's prime minister called a "secret atomic warehouse" in Tehran showed traces of uranium that Iran has yet to explain, two diplomats who follow the agency's inspections work closely say."

...

"Those traces were, however, of uranium, the diplomats said - the same element Iran is enriching and one of only two fissile elements with which one can make the core of a nuclear bomb. One diplomat said the uranium was not highly enriched, meaning it was not purified to a level anywhere close to that needed for weapons. "There are lots of possible explanations," that diplomat said. But since Iran has not yet given any to the IAEA it is hard to verify the particles' origin, and it is also not clear whether the traces are remnants of material or activities that predate the landmark 2015 deal or more recent, diplomats say."