The Pantheon was built in ancient Rome with a circular dome and rectangular portico. This version has all the same elements. Its columns are made from dowels while the elaborate Corinthian caps can be made using bits of duct tape on water-bottle caps. Using a series of cardboard boxes and containers will establish the proper dimensions. A plastic bowl is a quick way to make a domed roof.
Find Pantheon photos to use as models. (See Resources.)
Tape the three cardboard boxes shut. Tape the cylindrical container's lid to the cylinder. Glue the large rectangular box (which you can think of as A) to one end of the cylinder. Glue one of the smaller rectangular boxes (B) to the front of the large one and glue the other (C) to the bottom of the large one. If necessary hold the small box up temporarily with dowels. Glue the top of the plastic bowl to the cylinder's lid. Spray-paint everything white, including all the dowels and loose cardboard, and let dry completely.
Push pushpin into the bottom of the plastic bowl. Tie a length of the string to it. The length should reach two-thirds of the way to the bottom of the cylinder. Tie a marker to the end of the string and draw a line around the cylinder. Continue the line on the rectangular box glues to it. Shorten the string to one-third of the way from the bottom and repeat, drawing a line on the cylinder only Repeat on the plastic bowl, drawing seven consecutive rings from where the bowl is glued to the cylinder up to one-third of the way from the pushpin. This will be the domed section of the Pantheon. When done, remove marker, string and pushpin. Draw short vertical lines with straight edge perpendicular to the horizontal ones to look like building blocks.
Use the black marker and straight edge to draw a line from the midpoint of the top of the large cardboard box to the line at the side of the box. Repeat at the opposite end. Draw short vertical lines to replicate building blocks. Create a triangle of the exact same size on cardboard box B. Leave enough room near the bottom to write "M·AGRIPPA·L·F·COS·TERTIVM·FECIT." This is a section of the Pantheon's portico
Glue bottle caps to the end of the dowel. Take small double-sided pieces of duct tape and stick to each water cap to create the look of a Corinthian column head. Measure the distance between the bottom of box B to the bottom of box C. This will be the height of each dowel. There need to be 24 of them. When you have prepared all bottle caps, spray paint them white. Let dry. Measure where all the dowels will be positioned on box C. Cut an "X" at each. Glue the uncapped side of the dowel and stick through the "X" until it rests on the interior of the box. Glue the top of the bottle cap and stick to bottom of box B.
Cardboard boxes, containers and plastic bowl can be found at a restaurant-supply company.
Don't use plastic foam, as it melts when spray painted.