– Dec 10, 2007
| Number | County | Town | Size | Built | Verif | GPS | Description |
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| CO-03-01 | Arapahoe | Aurora | ? | 200 S. Chambers (Denver suburb) | |||
| CO-03-02 | Denver | 06-2005 | N39 44.83 W105 01.18 | In Denver. Bryant St. N. 0.1 miles from jct with I25 exit 210 in Denver to the hotel on the W. side of the road at 1975. Red Lion Hotel, round tower. | |||
| CO-03-03 | Denver | 1999 | 06-2005 | N39 44.64 W105 01.22 | In Denver. At the NW corner of I25 & Bus.I70 (CO40 or Colfax Av.). Mile High Stadium, oval bldg, open top. | ||
| CO-03-04 | Denver | 06-2005 | N39 44.72 W104 58.14 | In Denver. Bus.I70 (CO40 or Colfax Av.) E. 2.4 miles from jct with I25 exit 210 in Denver, N. on Franklin St. 0.35 (3 blocks) miles to the hospital on the W. side of the road. St. Joseph Hospital, round tower. | |||
| CO-03-05 | Denver | 06-2005 | N39 44.88 W104 58.10 | In Denver. Bus.I70 (CO40 or Colfax Av.) E. 2.4 miles from jct with I25 exit 210 in Denver, N. on Franklin St. 0.55 (5 blocks) miles to the hospital on the E. side of the road. Presbyterian St. Lukes Medical Center, oval tower. | |||
| CO-20-01 | El Paso | Pikeview | 12-2007 | N. of Pikeview. Interquest Pkwy E. 0.9 miles from jct with I25 exit 153 N. of Pikeview, N. on Voyager Pkwy 0.1 miles to the church on the E. side of the road at 11025. New Life Church, hexagon. (N38 59.51 W104 47.73) | |||
| CO-33-01 | Kit Carson | Burlington | ? | Polysided building used to house a carousel. | |||
| CO-50-01 | Pitkin | Snowmass | ? | Located in Gateway Subdivision, there are several modern round houses. Some of them consist of several units, with each round building a separate room and all rooms connected together with hallways. | |||
| CO-50-02 | Snowmass | ? | Situated atop a high bluff, it can be seen from CO82. Octagon house. | ||||
| CO-59-01 | Sedgewick | Julesburg | ? | S. of Julesburg, N. side of I76 | |||
| CO-64-01 | Yuma | Laird | 1880 | ? | Octagon farm house. |