a crypt under the floor of the church. Damaging and restoring Over the course of time and events (see above), the fresco has been damaged and subsequently restored. Much of the outer edge of the upper section, mainly architectural detail, is replacement work. Some regions of "new" paint can be clearly identified by differences in colour, visual texture and detail; and in certain places, by apparent "cracks" along the boundary between the original fresco surface, and areas of the design where the original surface is entirely absent and was repainted. The skeleton represents a memento mori, or reminder of death. Lower section The lower section, which depicts a skeleton in a tomb as a memento mori, has also lost significant paint. By this time, "standard practice" in restoration had become more conservative, with a stronger emphasis on preserving and revealing the authentic work of the original artist; whereas earlier restorations tended to have more focus on producing an aesthetically pleasing "recreation" of the artwork. As far as can be determined from available records, at the time when this painting was created no large-scale Roman-style coffered barrel vault, Triumphal arch or otherwise, had been constructed in Western Christendom since late antiquity. Notable characteristics The Trinity is noteworthy for its inspiration taken from ancient Roman triumphal arches and the strict adherence to recently developed perspective techniques, with a vanishing point at the viewer's eye level, so that, as Vasari describes it "a barrel vault drawn in perspective, and divided into squares with rosettes that diminish and are foreshortened so well that there seems to be a hole in the wall." This artistic technique is called trompe-l'œil, which means "deceives the eye," in French. The fresco had a transforming effect on generations of Florentine painters and visiting artists. The sole figure without a fully realized three-dimensional occupation of space is the God supporting the Cross, considered an immeasurable being. The kneeling patrons represent another important novelty, occupying the viewer's own space, "in front of" the picture plane, which is represented by the Ionic columns and the Corinthian pilasters from which the feigned vault appears to spring; they are depicted in the traditional prayerful pose of donor portraits, but on the same scale as the central figures, rather than the more usual 'diminution', and with noteworthy attention to realism and volume. Masaccio placed the horizon line across the floor between the two donors. Orthogonal