Search And Destroy: Area 51

Forgive me if this has been suggested before, But I haven't been on the forums for quite a long time. So anyways, Global Risk will of course try to defend all the secrets Area 51 has, While Black List, Of course destroys it. Global Risk will start at the Area 51 base, And Black List will start Underground [Underground like those santoria underground passages, but bigger]. The underground passage can lead 3 ways. The middle can lead to the middle [lol], the right can lead to A site, and the left can lead to b site. But, instead of me trying to explain it thoroughly, Can someone just send me a good program to make maps? That way i can show my idea more fluently