For the purposes of scientific topography observation of the natural features and outlines is followed by exact investigation of the architectural structures or remnants, a process demanding high technical competence, acute judgment and practical experience, as well as wide and accurate scholarship. The building material and the manner of its employment furnish evidence no less important than the character of the masonry, the design and the modes of ornamentation.
The products of the quarries of France for the five years 1901-1905 averaged 9,311,000 per annum in value, of which building material brought in over two-thirds.
Much of the building material is a brown sandstone obtained from quarries only 3 m.
For the architectural embellishment of the city the finest building material was procurable without difficulty and in abundance; Pentelicus forms a mass of white, transparent, blue-veined marble; another variety, somewhat similar in appearance, but generally of a bluer hue, was obtained from Hymettus.
Numerous ruins, an amphitheatre, still recognizable, a theatre, a temple of Augustus, &c., existed in the 16th century, and have been since used for building material.
