Analysis of the surfaces of the walls and the building techniques and materials, showing up the restoration stages and the repair works

Although the remains which can be seen today correspond to what was left of the medieval walls and their later reconstruction, some possible stages in its construction can be dated and the different types of masonry present in the wall will be dealt with further on.

Possible construction stages of the Segovian Walls
1 - Roman
As already mentioned in another section, Segovia must have had remains of a High Empire wall. The city probably had a fence which would have protected the area of the present walls. The only vestiges which can be assigned to this period are the opus quadratum granite ashlars that Merino de Caceres found in the foundations of a tower where the Alcazar stands.
Remains of the Low Empire period can be guessed at around the San Andres area. These would be foundations of granite ashlars on top of the rock on the first row of walls.
An interesting element is the use of funerary stelae coming from at least two necropolises.
When were these ashlars used as secondary material?
Are there two phases in the re-use of this material or only one?
In the 4th Century, during the Low Empire period, the need to construct city walls entailed the use of different materials, such as tombstones.
Necropolises were used as quarries even in medieval times.
2 - Muslim
There are no remains which allow us to identify the stone decorations with Califal or Emiral works, except for the vestiges of the walls and the fact that any urban nucleus had to erect a wall or a fence, particularly a border town like Segovia.
3 - Re-erection of the walls
Most of the design of the walls corresponds to the fortification works ordained by Alphonso VI, and directed by Raimundo de Borgona in 1088.
The term re-erection is used because it is thought that they were built on top of a ruined wall. In the historical section, we put forward the idea that Segovia became a border town in medieval times. Christian raids must have allowed occupation of the city at the beginning of the 11th century, since it was attacked by the Toledan Muslims who destroyed part of the aqueduct. Before the Christians took Toledo in 1085, Segovia must have been a Christian stronghold. Most of the construction was carried out between 1088 and 1122 by Christian and Muslim workers.
A system of moats was laid in the Alcazar area and even some wooden elements to help build up the defence.
4 - Enlargement and reinforcement
This process took place from the 12th to the 15th centuries. Raimundo de Borgona's fence would have been reinforced and made higher. This was the most important period for the walls of Segovia. We know of its role as a Court and its intervention in the political conflicts of the time. The works done to improve the Alcazar and the clerecía, parallel to the wall, are well documented.
5 - Repairs
In the historical section, the continuous efforts to occupy the wall spaces in the 15th and 16th centuries were noted.
The repairs carried out under the Catholic monarchs (e.g. those of the San Andres gate), indicate that there was progressive abandonment of the walls. The War of Comunidades (1520-1521) meant massive destruction of the fortress due to its opposition against the Emperor Charles V.
6 - Repairs
The 17th and 18th centuries coincided with the decline of the walls and the loss of their defensive function. Contracts were signed to carry out a lot of repairs and maintenance work to solve the problem of sections of stones falling, as had happened on the north apron wall.
7 - Ruins
During the 19th century, the walls became a problem for development of the city and they were also in a ruined state. This led to demolition and looting of the walls and gates, as well as their characteristic elements. This situation continued during the first part of the 20th century.
8 - Restoration and consolidation
Starting from the 1940s and after democracy had been restored and political independence gained, protection and restoration of the walls were guaranteed.

Construction techniques:
The variety of interventions show up different types of works. The medieval technique is the opus emplectum, the external and internal adornments are made using opus incertum masonry aggregated with lime and sand. The web of the wall consists of low quality compact materials.
Towers and blocks reinforce the walls and the openings are framed with ashlars. These ashlars were either taken from existing ruined buildings or from quarries near Zamarramala.
There are holes in the upper part of the walls, which indicate that these parts were made with the aid of embedded scaffolds.
The Mudejar pattern is common in the gates and opus latericium in the crown of the towers around San Andres. The crown of the wall was originally made of crenels and merlons built to protect the parapet walk and the guard post.
We do not know whether the walls were plastered, but there are at least remains of esgrafiado and late medieval paintings of the Alcazar.
Later repairs were made using masonry with different kinds of mortar, depending on the budget the workers had. There were also indiscriminate mixtures of filling material.

Types of materials:
Granite: this came from the mountain quarries and was also used to build the aqueduct. It was laid in opus quadratum with perforations so that it could be lifted by cranes.
In the 16th century, the granite quarries were exploited to build Segovian palaces, using smaller quadratum and viatum for this purpose.
Limestone: medium grain, highly meteoric and mainly used in Romanesque buildings, taken from quarries located 1 km to the north.
Grit: laid mixed with pebbles.
Masonry: made of limestone and mixed with filling materials.
Ashlars: used as cornerstones for the base of the wall and also as defensive elements, where the walls needed to be well set, or where they were subject to easy attack.
Brickwork: normally solid bricks made of local clay and baked in local brick kilns. Bricks coming from ruined buildings were re-used in repair work.
Filling materials: tombstones, fragments and broken bits from ruined buildings, etc.

Methods of intervention:
The variety of interventions, repairs and restoration works on the walls can only just be singled out. They began at the end of the Modern Age and concerned unsafe or damaged sections, using masonry or filling material.
Restoration works during the 20th century had the purpose of giving some dignity to the ruined walls, with preservation and rebuilding interventions like those which can be seen at the San Juan gate, in the Alcazar and in the reconstruction of merlons.
According to modern criteria, current restoration tries to make it easy to distinguish between the old and new parts, and between materials and techniques. Examples of this having been accomplished are the Provincial Museum and the latest intervention on the northern walls near the Santiago gate.