Everywhere I look I'm seeing cloches. Although I can't make perfect cylindrical glass domes, I can approximate the idea with dollar stores frames. Check it out.
4 - 5x7" frames
2 - 4x6" frames
carpenter's wood glue
2 wooden curtain rings
2 small round mirrors
white acrylic paint
brown shoe polish
hot glue gun
When I bought these frames at my local dollar store I stood in front of the frame aisle and tried different combinations until I found the right fit. This works because the 5x7 frames have thick wooden areas and the 4x6 ones have thin ones. You may find other combinations of sizes that work as well.
Strip out the frames.
Attach the 4x6 frames together along a very thin edge of the 6" sides. Attach the other 6" sides to the top of the cube. This will form the roof of the greenhouse.
Clamp with tape until the glue has dried and set up.
Fill the gap formed at the peak of the roof with a piece of 1/2" by 1/2" wood, the length of the roof. I cut my wooden filler out of a piece of 1/2 plywood but you might be able to find a piece of molding at your local lumber yard to fit. (since you are covering this, you could use styrofoam or several strips of foam core)
Fill the two triangles at the ends of the roof with mat board.
Cut a length of mat board the length of the roof and 2" wide. Use a penny to trace a series of scallops along one long side. Cut out. Punch a hole in the center of each scallop. Score a line one inch above the opposite long edge and fold. Carefully remove the center cardboard so that you have two paper wings. Glue over the wooden filler to form the gingerbread decoration on the roof peak.
Cut two thin strips of mat board to cover the gaps formed where the roof meets the cube.
I glued small round mirrors that I found at Michael's to the back of small wooden curtain rings then glued them to the center of the mat board triangles.
Cover a white pillar candle with a page from an old book, wrap with twine and hot glue a vintage game piece over the knot. Black paper butterflies (a Martha paper punch) are glued to the candle as well.
The cloche was painted with several coats of white acrylic paint inside and out. When dry, I rubbed brown shoe polish over the entire surface, buffing off for an antique look. Lastly, I replaced the glass then added a small dollop of hot glue at each corner to secure.
The cloche was placed over my altered candle and I welcomed the many oohs and aahs. (mainly from me)