Is Minas Tirith of Gondor modelled after the great Noldorin city of Gondolin? Because they definitely look alike, except I'm guessing Gondolin would be 10 times bigger.
It seems Tolkien said little about the structure of Gondolin. Indeed, according to this answer, the only city described in detail in Tolkien's works is Minas Tirith.
However, from Wikipedia we have the following description of Gondolin. The only concrete link I've found to the structure of Minas Tirith is its seven gates.
Within the Echoriath, the Encircling Mountains, lay a round level plain with sheer walls on all sides and a ravine and tunnel leading out to the southwest known as the Hidden Way. In the middle of the vale there was a steep hill which was called Amon Gwareth, the "Hill of Watch". There Turgon decided to found a city [Gondolin], designed after the city of Tirion in Valinor that the Noldor had left.
The Hidden Pass was protected by seven gates, all constantly guarded; the first of wood, then stone, bronze, iron, silver, gold, and steel.
Which is reminiscent of the following description of Minas Tirith:
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 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 the paved way that climbed toward the citadel turned this way and that and then that across the face of the hill.
-- The Return of the King, Chapter 1: Minas Tirith
Minas Tirith had seven (big and main) gates in seven concentric walls around the center of the city.
Gondolin apparently had only one main wall, and the seven gates were sequential gates within the narrow pass which lead through the mountains into the hidden valley where Gondolin was. The seven gates were not actually parts of the hidden CITY of Gondolin but were on the border of the hidden KINGDOM of Gondolin.
The city of Gondolin was built on a relatively level hilltop and had many small and large streets and courts. Minas Tirith had seven different concentric levels and each level had one main concentric street and many smaller radial streets or alleys.
There were a number of similarities. Gondolin and Minas Tirith were both on hills. The royal palace at the center of Gondolin included or was next to the Tower of Turgon. The royal palace at the center of the central circle of Minas Tirith included or was next to the White Tower or Tower of Ecthelion. The Tower of Ecthelion by the Court of the Fountain in Minas Tirith was named after a Steward of Gondor who in turn was ultimately named after Ecthelion of the Fountain, who died fighting a Balrog in the fountain in the court before the royal palace in Gondolin.
So in some ways Minas Tirith was designed as an imitation of Gondolin. Minas Tirith was also sort of a cheaper imitation of Osgiliath, the original capital of Gondor, which in turn was partially a cheap imitation of the capital city of Numenor, which in turn was partially a cheap imitation of Gondolin, which in turn was partially a cheap imitation of Tiron.