[@1Charak2]

I don't think that I should name drop spoilers of Fate/Extella and FGO here, but Excalibur can and did defeat threats that scared (as in made them feel like running to the reverse side of the world) even the actual gods (the ones that have divine authorities, not just divinity). To date, there's no example of anything in the franchise that stood in the way of a properly released Excalibur and hadn't been evaporated.

The fact that the Gardens are Anti-World and belong to an Evil Servant, actually allow Saber to release extra Seals of the sword if she ever felt like shooting it down, so the power we usually see would be greatly amplified when used against the Gardens.

Lastly, Camelot is the actual strongest fortification in the franchise so far. Perhaps only losing to Ozy's buildings and Uruk's walls during the Babylonia Singularity, but that's debatable. The fact is that, at most after these two, Camelot is the absolute best fortification in the setting.