Can I make ICBM´s to destroy cities?
it would be more realistic.

nope

And unless the city is very small nukes DO NOT destroy cities completely!!!!!
It might be fun to make nukes destroy cities but not more realistic.

Too bad there isn't something that could level an entire city. A special futuristic nano-bomb os something. Like a flag similiar to nukes.

Like the "Planet Buster" from SMAC ;)!

I mean that when you nuke city so much that it is size 1
you should be able to destroy it.

And it would be more realistic because real nukes can have
up to 10! individually targeted warheads it would surely destroy
a city.

And if an city would survive from nuclear attack,
it would be just a piece of junk. I think that every city
that is in size smaller than 20 km could be destroyed with one
multi-warhead ICBM.

For example a A-bomb dropped to Hiroshima was 50kt
and 50-80% of buildings were completely destroyed.

Modern warheads are much more poverfull.
Usually todays nuclear weapons are about from 100kt to
2Mt.

And it would be more realistic because real nukes can have up to 10!
Ten what? What do you mean?

individually targeted warheads it would surely destroy a city.
Are you sure? Maybe if you hit a city with many many 5 megaton nukes it would probably destroy the city. How many nukes does it take to get to the center of a small city (tootsi roll)? Honestly I don't know but it would definitly take more then one nuke to destroy a city. Obviously if you hit a dinky town in the middle of no where that is just a few hundred poeple (size one city) you should be able to destroy it pretty easily.

Akumaster,first of all u must read more about history.The bomb droped on Hiroshima was 20 kt.You are right about modern nuclear weapons starting power (100 kt), but u are wrong about their final power.It is about 15 Mt.
Now some words to Subss.I see that u have little idea about nuclear weapons and their power.What do u mean 'many many 5 megaton nukes would probably destroy a city' ?For example,one 5 Mt nuke destroys everything in about 5 mile radius and heavy damages other buildings away for about 2 more miles.But that was really primitive example , because the effect of the blast enourmously varies
depending the blast was in the air,on ground or even underground.The most damage generated from the bomb is ,then the bomb is detonated 500 meters above the ground (in the air).
P.S.
Subss,you didn't understand what Akumaster meant - 'real nukes can have up to 10!' .He mean't that single warhead can carry about 10 smaller warheads,which means that smaller ones are droped then the main warhead reaches it's target.