Nothing remains of the exterior of Lescot’s Louvre.
The general features, including the corner pavilion, were copied faithfully in the 17th century, both by Lemercier and Le Vau in the extensions they made. However, with the remodelling of the southern façade by Perrault, and the completion of the Grand Louvre project by Viconti and Lefuel, the exterior features of Lescot’s project were lost.
As may be recalled, Lescot finished only less than half of his original plans for a royal urban palace. The northern and eastern wings were still medieval by the time he died in 1578. However, the western and southern wings showed Lescot’s intent. They were joined by a massive corner pavilion, which became known as the pavilion du roi. Presumably, the design of this pavilion was supposed to be copied at the four junctions of the courtyard palace.
Unlike the exuberant design of the courtyard façade, the exterior facades were austere. The windows of the first floor were capped by triangular pediments, but the design was otherwise quite plain.
The design of the pavilion followed the same pattern at the lower floors, but the top storey had low relief carvings and was capped by a pediment, which also featured reliefs, and a French sloping roof. Stone quoins were inserted at the corners.
The design seems to have been a bit top-heavy, but it is possible that the pavilion was primarily meant to be enjoyed directly from the garden below, as opposed from across the river.
The austerity of the outer façade was likely meant to represent the masculine and impenetrable qualities of the monarchy. As with Florentine palaces, the courtyard represented private enjoyment, the exterior was meant to denote strength.
For more information, see the following links: http://mexichino-jr.blogspot.com/2011/03/lescot-wing.html, http://mexichino-jr.blogspot.com/2011/08/louvre-in-paris-lemercier-pavillion-de.html