Labyrinth

We think of a labyrinth as a maze, with branching passages making it easy to lose your way. But in the middle ages, a labyrinth usually meant a very specific pattern:

This pattern has no branches to get lost in. You enter, weave back and forth, in and out, and eventually reach the center. You weave back and forth seven times. 

There are a lot of rock structures like this on beaches all around Europe. Some people think it was a kind of fish trap, where the fish would swim in and then not be able to find their way back out. They are also carved in stones and built of tiles on the floors of cathedrals. I saw an old one in Glendalough.

                              

This was identified with the city of Jericho: Joshua had to march his army around the city seven times, blowing his trumpets, to bring the walls down. Here's an example, but there are tons of these illustrations in medieval manuscripts.

Castles are built along these kinds of lines. You have to climb a hill to reach most castles, which means some switchbacks. The longer the path, the more opportunity defenders have to rain arrows down on attackers before they reach the gates. You can get a visceral feel for this playing Bloons Tower defense:

And then, once you are inside the walled city, the gate of the city is usually not in a straight line with the gate of the castle wall or with the inner keep, for the same reason. Here is one of the first castles I ever visited, Hohenzollern. See how you spiral around and around to get in:

So I think Tolkien, being familiar with all this, designed Minas Tirith along these lines. You have a solid intersecting line protruding from the center of the city out all the way to the gate a "towering bastion of stone, its edge sharp as a ship-keel" and then "seven levels" so the "paved way that climbed toward the Citadel turned first this way and then that" exactly as the labyrinth:

For the fashion of Minas Tirith was such that it was built on seven levels, each delved into the hill, and about each was set a wall, and in each wall was a gate. But the gates were not set in a line: the Great Gate in the City Wall was at the east point of the circuit, but the next faced half south, and the third half north, and so to and fro upwards; so that the paved way that climbed towards the Citadel turned first this way and then that across the face of the hill. And each time that it passed the line of the Great Gate it went through an arched tunnel, piercing a vast pier of rock whose huge out-thrust bulk divided in two all the circles of the City save the first. For partly in the primeval shaping of the hill, partly by the mighty craft and labour of old, there stood up from the rear of the wide court behind the Gate a towering bastion of stone, its edge sharp as a ship-keel facing east. Up it rose, even to the level of the topmost circle, and there was crowned by a battlement; so that those in the Citadel might, like mariners in a mountainous ship, look from its peak sheer down upon the Gate seven hundred feet below. The entrance to the Citadel also looked eastward, but was delved in the heart of the rock; thence a long lamp-lit slope ran up to the seventh gate. Thus men reached at last the High Court, and the Place of the Fountain before the feet of the White Tower: tall and shapely, fifty fathoms from its base to the pinnacle, where the banner of the Stewards floated a thousand feet above the plain.

Further evidence for this is the resemblance between "Minas" and "Minos" the king who had the labyrinth built-- although in his invented etymology, the name means Watch Tower.

The word transliterated into ancient Greek as labyrinthos is more like dapurito which, if I've got the syllabary right, looked like this in Linear B:

The palace at Knossos is from the bronze age, so is plausibly from the right place and time for the Theseus/Minos/Ariadne myth. While it doesn't contain a labyrinth as such (although the original meaning of labyrinth may just be a big complex with a bunch of rooms, which, sure) it does have a lot of bull-related decorations.