Title: Spirangle
Content:  Three-dimensional spirangles have layers that slant upward, progressively gaining height from the previous segment. This is similar to staircases in large buildings that turn at the top of each flight. The segments also may progressively lose an amount of length and resemble a pyramid.
Title: Mingachevir Church Complex
Content:  The Temple 3 was built on the site of the Temple 1. This temple is one-story basilica with worship hall. On the eastern wall of the temple, there is a semi-circle. The main feature of the Temple 3 is extremely thickness of walls. Thus, the walls of the temple have a thickness of 2.05 meters. The thickness of the walls of the Temple 2 does not exceed 1,3 meters. The Temple 4 was built on the ruins of the Temple 3. This temple consists of two distinct parts including the oldest southern part with three smaller rooms and the northern part of the church and the narthex. 
Title: Ħal Saflieni Hypogeum
Content:  The Hypogeum is constructed entirely underground and consists of three superimposed levels hewn into soft globigerina limestone, with its halls and chambers interconnected through a labyrinthine series of steps, lintels and doorways. The upper level is thought to have been occupied first, with the middle and lower levels expanded and excavated later. Some of the middle chambers appear to share stylistic characteristics with the contemporaneous Megalithic Temples found across Malta.
Title: Tour Mélusine
Content: The ground floor of the tower was used as a cellar for storing food supplies. It is not accessible to the public. ; The second level was originally accessible by a mobile ladder, now replaced by a stone staircase. ; The third and fourth levels are accessible by a metal staircase (previously made of stone) and each has a vaulted dome. The third level allowed access to the wall walk. ; The fifth and final level corresponds to the terrace at the top, hence a view of the fortified city, the forest of Mervent-Vouvant and the surroundings is impressive. The Tour Mélusine consists of a total of five levels: 
Title: Minarets of the Temple Mount
Content:  by earthquakes. The minaret is divided into several stories by stone molding and stalactite galleries. The first two stories are wider and form the base of the tower. The additional four stories are surmounted by a cylindrical drum and a bulbous dome. The stairway is externally located on the first two floors but becomes an internal spiral structure from the third floor until it reaches the muezzin's balcony. The minaret is excavated into the naturally occurring layer of bedrock in the northwest corner of the Haram. It is partitioned into several 'stories' by stone molding and muqarnas (stalactite) galleries. The first two stories are wider and 
Title: Minaret
Content:  The basic form of minarets consists of four parts: a base, a shaft, a cap and a head. Minarets may be conical (tapering), square, cylindrical, or polygonal (faceted). Stairs circle the shaft in a counter-clockwise fashion, providing necessary structural support to the highly elongated shaft. The gallery is a balcony that encircles the upper sections from which the muezzin may give the call to prayer. It is covered by a roof-like canopy and adorned with ornamentation, such as decorative brick and tile work, cornices, arches and inscriptions, with the transition from the shaft to the gallery typically displaying muqarnas.
Title: Castle of Monsanto
Content:  The fortress consists of three walled courtyards: an outer irregular exterior wall that encircles two other lines of walls. These segments, with staircases to access the adarve, lack merlons. The enclosure includes a main door preceded by Casa do Guarda (guardhouse), a rectangular floored compartment, with arched eastern access door. In the interior, there is an archway, surmounted by an orifice for the coat-of-arms, flanked by an armillary sphere. On the right hand side is an inscription that is indecipherable. On the northern elevation are three cross-sectional bombardments, one on the northeastern angle. The main arched gate in the north covered by vaulted ceiling and false door on the south tower. The enclosure includes four towers attached 
Title: Murney Tower
Content:  The tower stands surrounded by a dry-ditch and is accessible only by a bridge. When the tower was originally built, there was no bridge to cross the dry-ditch. It is likely that soldiers would have accessed the tower through two ladders placed in the ditch. Murney Tower was constructed with locally quarried limestone with special brickwork on the barracks and basement levels of the tower's interior. On the thickest side the walls are about 15 ft. thick at the base and 13 ft. thick up top. On the weaker side the walls are about 8 ft. thick. The walls are thicker on the south side because a 
Title: St Robert's Church, Pannal
Content:  The tower is in perpendicular style, in three exterior visual stages separated by stringing. On different levels it has three interior floors consisting of the vestry and its loft at the bottom, then a clock chamber whose floor is roughly level with the nave ceiling, and a bell chamber on the top floor. The bottom and middle floor levels are indistinguishable from the outside, because the diagonal buttresses run up the bottom two stages and half of the top stage, and there is exterior stringing halfway up the bottom floor but not between the bottom and middle floors. However, stringing on the exterior identifies the floor level of the bell stage. The interior chambers of the tower 
Title: Tower of Gömeç
Content:  It was bolted on the inside with a beam and two bars and by a single beam on the outside. On the inside walls of the tower, there are beam holes for the floorbeams of the four levels - the lowest are directly above the door lintel. On the first, third and fourth floors, the beams ran north–south, on the second floor they ran east–west. The top floor was the viewing platform, which was surrounded by two layers of stone blocks and crenellations. These are almost completely intact, with the saddle-shaped tops of the merlons still preserved in some cases. Around the tower are the ruined walls of various buildings, including an olive oil press.

Question: what are the 3 layers of the meninges?
Answer: the arachnoid mater.
arachnoid mater.
pia mater.
the pia mater.
dura mater.