Frame locks, from ABUS or the Basta "Click" (my favourite)
I've been surprised that they aren't popular here.
Yes, most people like to lock their bikes to something, but so many of the stolen bikes are left unlocked and ridden off.
It depends a bit on the value of the bike. Most thefts of $50 bikes are opportunistic.
One pretty much needs a bank vault to keep a $10,000 bike safe.