In Panini's day, as in our own, the Pantheon was one of the great tourist attractions of Rome. Built under Hadrian in the 2nd century, this monumental domed temple has survived intact, owing to its consecration as a Christian church—Santa Maria Rotunda—in AD 609. Panini's depiction is populated with foreign visitors and a lively mix of Romans from all social strata who congregate in the Pantheon to pray, to chat, and to admire the wondrous architecture.
Trained in architecture and theatrical design, Panini manipulated the perspective to show a larger view of the interior than is actually possible from any single place. The viewpoint is deep within the building, facing the entrance. The portals open to the colossal columns of the porch and a glimpse of the obelisk in the piazza before the church. Through the oculus in the center of the dome, Panini revealed the bright blue sky flecked with clouds.
As Canaletto was to Venice, so Panini was to Rome. Both artists documented with exacting skill and vibrancy the monuments of their cities and the daily comings and goings of the inhabitants. In this case, Panini depicted the classical landmark that inspired the design of the Rotunda in the National Gallery's West Building.
More information on this painting can be found in the Gallery publication Italian Paintings of the Seventeenth and Eighteenth Centuries, which is available as a free PDF https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/italian-paintings-17th-and-18th-centuries.pdf
on the collar of the dome: [LAVDATE] DOMINVM IN SANCTIS EIVS LAVS EIVS IN ECCLE[SIA SANCTORVM]
The Dowager Countess of Norfolk; (Christie, Manson & Woods, London, 20 November 1925, no. 69); bought by (William Sabin, London); sold presumably by him to (Count Alessandro Contini Bonacossi, Rome); purchased October 1927 by Samuel H. Kress [1863-1955], New York; gift 1939 to NGA.
- Il Settecento Italiano, Palazzo delle Biennali, Venice, 1929, no. 32, no. 12.
- Loan for display with permanent collection, Fogg Art Museum, Cambridge, Massachusetts, 1931-1932.
- An Exhibition of Italian Paintings Lent by Mr. Samuel H. Kress of New York to Museums, Colleges, and Art Associations, travelling exhibition, 24 venues, 1932-1935, mostly unnumbered catalogues, p. 27 or p. 31, repro.
- Masterpieces of Art. European & American Paintings 1500-1900, New York World's Fair, 1940, no. 37.
- Art in Rome in the Eighteenth Century, Philadelphia Museum of Art; The Museum of Fine Arts, Houston, 2000, no. 266, repro.
- L'Antiquité rêvée. Innovations et résistances au XVIIIe siècle [Antiquity Revived. Neoclassical Art in the Eighteenth Century], Musée du Louvre, Paris; Museum of Fine Arts, Houston, 2010-2011, no. 35 and repro. (French cat.), not in English cat. (shown only in Paris).
The support is a fine, plain-weave fabric. The ground is a reddish terracotta-colored layer that contains large aggregates of translucent white pigments. It is exposed in the spandrels of the arched top. In the top third of the composition a warm gray-brown layer was applied over the ground; in the bottom third, under the floor, there is a cooler, lighter gray layer over the ground. In the ceiling the red tone of the ground remains visible as highlights; in the floor it remains visible at the edges of the figures to set them off and soften the transition from the dark clothing to the lighter floor. The gray underlayer is similarly used as shadowing around the eyes of the figures.
Using a straightedge, lines were incised into the gray-brown layer as guides for the placement of the coffers in the ceiling; similar lines were also used to place the floor tiles and set the perspective. A stylus was used to define the contour of the coffered ceiling. Only the letters in the inscription seem to have been incised into the wet paint freehand. The composition appears to have been sketched in before the lines were incised and the paint applied: the incised floor lines stop precisely at the edges of some of the figure groups. This careful planning seems to have eliminated the need for significant alteration in the painting process. Artist's changes are limited to the sculptures in the niches and to the position of the font to the left of the doorway. Several figures, however, such as the monk in a white cowl at left center, were painted over the floor designs, revealing that some changes were made late in the development of the composition.
The paint was applied using small brushes and fluid, brushmarked strokes, generally wet-into-wet and in opaque tones, for the basic color and forms of both architecture and figures. Precise architectural details were painted over the general forms of the building, probably with the use of a straightedge and compass. The figures are more broadly painted than the architecture, with details, shadows, and highlights quickly sketched over the opaque basic tone that gives them general form and modeling. Often the brush was held so that one side was more heavily loaded than the other, creating strokes and highlights in one application. The rich, varied textures of marble and stone were suggested by stippling and by dragging the dry brush through wet paint.
Although most of the tacking margins have been removed, remnants of the unpainted fabric are present and the painted image appears to retain its original dimensions. The black costumes are abraded and there are minor losses at the edges of the painting. The painting was relined by Stephen Pichetto about 1930. Removal of overpaint and discolored varnish during treatment by Ann Hoenigswald in 1992 has revealed the original design of the composition, an arched top within the rectangular canvas. The unpainted spandrels were painted out to the edges after 1925, possibly in 1930. Scientific analysis identified modern pigments in these areas.
 X-radiographs confirm Panini's practice of changing his preliminary design by the addition of figures and adjustments to the trabeation. See also Cleaveland Museum of Art 1982, 383, for a discussion, based on x-radiographs of the museum's 1747 version of the subject, of similar compositional changes made after the initial layout was established.  The 1925 sale catalogue (see provenance) refers to the painting as having an arched top.
- Gaunt, William. Rome Past and Present. London, 1926: 7, color pl. 69.
- Preliminary Catalogue of Paintings and Sculpture. National Gallery of Art, Washington, 1941: 146, no. 135, as The Interior of the Pantheon.
- Book of Illustrations. National Gallery of Art, Washington, 1942: 242, repro. 162, as The Interior of the Pantheon.
- Paintings and Sculpture from the Kress Collection. National Gallery of Art, Washington, 1945 (reprinted 1947, 1949): 142, repro., as The Interior of the Pantheon.
- Einstein, Lewis. Looking at Italian Pictures in the National Gallery of Art. Washington, 1951: 108, repro. 110.
- Cairns, Huntington, and John Walker, eds., Great Paintings from the National Gallery of Art. New York, 1952: 74, color repro., as The Interior of the Pantheon.
- Paintings and Sculpture from the Samuel H. Kress Collection. National Gallery of Art, Washington, 1959: 254, repro., as The Interior of the Pantheon.
- The National Gallery of Art and Its Collections. Foreword by Perry B. Cott and notes by Otto Stelzer. National Gallery of Art, Washington (undated, 1960s): 24, repro.
- Arisi, Ferdinando. Gian Paolo Panini. Piacenza, 1961: 161-162, no. 136, figs. 186-187.
- Brunetti, Estella. "Il Panini e la monografia di F. Arisi." Arte Antica e Moderna 26 (1964): 182.
- Summary Catalogue of European Paintings and Sculpture. National Gallery of Art, Washington, 1965: 99, as The Interior of the Pantheon.
- Cairns, Huntington, and John Walker, eds. A Pageant of Painting from the National Gallery of Art. 2 vols. New York, 1966: 2:328, color repro.
- European Paintings and Sculpture, Illustrations. National Gallery of Art, Washington, 1968: 87, repro., as The Interior of the Pantheon.
- Fredericksen, Burton B., and Federico Zeri. Census of Pre-Nineteenth Century Italian Paintings in North American Public Collections. Cambridge, Mass., 1972: 157.
- Shapley, Fern Rusk. Paintings from the Samuel H. Kress Collection: Italian Schools, XVI-XVIII Century. London, 1973: 122, fig. 242.
- European Paintings: An Illustrated Summary Catalogue. National Gallery of Art, Washington, 1975: 258, repro., as The Interior of the Pantheon.
- Wixom, Nancy Coe. "Panini: Interior of the Pantheon, Rome." Bulletin of the Cleveland Museum of Art 62 (1975): 265-267, fig. 2.
- Shapley, Fern Rusk. Catalogue of the Italian Paintings. 2 vols. Washington, 1979: I:349-351, II:pl. 254, as Interior of the Pantheon.
- European Paintings of the 16th, 17th, and 18th Centuries: The Cleveland Museum of Art Catalogue of Paintings, part three. Cleveland, 1982: 384.
- Walker, John. National Gallery of Art, Washington. Rev. ed. New York, 1984: 346, no. 476, color repro., as Interior of the Pantheon.
- European Paintings: An Illustrated Catalogue. National Gallery of Art, Washington, 1985: 298, repro.
- Arisi, Ferdinando. Gian Paolo Panini e i fasti della Roma del '700. Rome, 1986: 373, repro., no. 283, pl. 129 (detail).
- National Gallery of Art. National Gallery of Art, Washington. New York, 1992: 118, repro.
- Arisi, Ferdinando, ed. Giovanni Paolo Panini 1691-1765. Exh. cat. Palazzo Gorico, Piacenza. Milan, 1993: 40-41, repro.
- Bowron, Edgar Peters. "The Kress Brothers and Their 'Bucolic Pictures': The Creation of an Italian Baroque Collection." In A Gift to America: Masterpieces of European Painting from the Samuel H. Kress Collection. Exh. cat. North Carolina Museum of Art. Raleigh, and New York, 1994: 43, fig. 2.
- De Grazia, Diane, and Eric Garberson, with Edgar Peters Bowron, Peter M. Lukehart, and Mitchell Merling. Italian Paintings of the Seventeenth and Eighteenth Centuries. The Collections of the National Gallery of Art Systematic Catalogue. Washington, D.C., 1996: 189-193, color repro. 191.
- Wilkins, David G. and Bernard Schultz and Katheryn M. Linduff. Art Past-Art Present, New York, 1997, no. 3-117, repro.
- Hill, Claudia. “Sanctuary." In Encyclopedia of Comparative Iconography: Themes Depicted in Works of Art. Edited by Helene E. Roberts. 2 vols. Chicago, 1998: 2:787.
- Hand, John Oliver. National Gallery of Art: Master Paintings from the Collection. Washington and New York, 2004: 243, no. 193, color repro.