A missile silo is a underground vertical cylindrical container for the storage and launching of ICBMs. They typically have the missile some distance under the surface, protected with a huge "blast door" on top.

Until the 1960s ICBMs had been launched from surface bases. The Soviets used completely aboveground launchers similar to those found at a spaceport, which made them vulnerable to US bomber attack. The US Atlas missile used four basing schemes. The first were vertical, above ground launchers at Vandenberg AFB, CA. The second was stored horixontally in a warehouse-/shedlike structure with a retractable roof at Warren AFB, WY. The third was somewhat better protected, stored horizontally in a concrete building known as "coffins", then raised to the vertical shortly before launch. These rather poorly protected systems were a side effect of the corrosive liquid fuels used, which required the missiles to stand empty and then be fueled immediately prior to launch. The fourth version of the Atlas ICBM (the Atlas F) were stored vertically in underground silos. The Atlas was fueled in the silo and then had to be raised to the surface for launch, it could not be launched from within the silo. The Titan I missile used a similar silo basing scheme as the Atlas F.

Things changed with the introduction of the US's Titan missile and the Soviet UR-100 missile series. Both used new liquid fuels that could be stored in the missiles, thereby allowing for rapid launch. Both systems were then moved to the silo system. The introduction of solid fuel systems in the later 1960s made this even easier.

The silo has remained the primary basing system for land based missiles since that time. However the increased accuracy of inertial guidance systems has since rendered them somewhat less protected than they were in the 1960s. The US spent considerable effort in the 1970s and 80s designing a replacement, but none of the complex systems were ever produced. Both the US and USSR developed mobile ICBM's as well, but only the Soviets put them into production:

• MPS (Mobile Protective Shelters) plan, in which 200 MX missiles would be shuttled around between 4600 soft shelters.
• Midgetman missile
• one version of the Topol-M

Today much of the US arsenal has been placed on submarines (as SLBMs), while Russia has downsized their own force to a handful of mobile and silo-based weapons.

On a lighter note, the increase in decommissioned missile silos has led governments to sell them to individuals, who then convert them to indisputably unique abodes.