FORT

[noun] [C] - a military building consisting of an area enclosed by a strong wall, in which soldiers live and which is designed to be defended from attackThe US cavalry rode into the fort and the gates closed behind them.The remains of the Roman fort are well preserved.If something is like Fort Knox, it is impossible to enter it illegally or steal anything from it.His shed has so many locks and bolts it should be as safe as Fort Knox.