I am DMing a group of five players in a long term game with D&D 3.5e and players are the leaders of a nation (One of them is the king actually). They are now very close to start a war with another nation and they are setting up strategies for upcoming conflict. One of them (Wizard Level 17) came up with an idea which is about opening a gate or a portal to transport their army to a strategic location, lets say near their enemy's capital city and asked me if there is such a spell. I liked the idea because it leads to other campaign ideas like "Wizard tires to find a long forgotten ancient spell" in which players tries to find an ancient tomb or library and clears it to find the spell or "Battle of Gate Defense" in which players tries to pass their army safely through the gate while defending it from enemy trying to close it. Although I know about "Teleport" (teleports limited number of individual) and "Gate" (teleport to "different" plane") spells, I haven't ever come up to any spell that creates a massive gate an army can pass through and teleports to another location in "same plane" (material to material in this condition).
In conclusion, I wanted to ask if there is a spell creates a kind of portal which can transport a "vast number of individuals" to a location in "same plane". Although I mentioned that we are playing 3.5e, suggestions from different editions of D&D are appreciated, because I may think about adapting it to 3.5e.