ArandorЕсли я правильно помню ишью о столице, то там сказано, что под землей располагаются государственные строения, т.е. не весь город под землей, а лишь часть.

3. "I can accept and even approve of having a capital city," says @@RANDOMNAME@@, a military strategist. "But we'd be putting all our eggs in one basket if we choose somewhere too vulnerable! Believe me, capitals always get the brunt of the enemy attack because of their political and economic importance. We should put aside a few billion @@CURRENCY@@s and build our capital city underground. They'll never bomb us there!"