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$10,000,000

  • For Sale
  • Active
  • Single Family
  • 7 Beds
  • 3 Full Baths
  • 2 Partial Baths
  • 6,988 Sq. Ft.
  • 3 Car Garage
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Exquisite secluded sanctuary in the heart of Carolyn Heights. Tucked into one of Boulder's most prestigious enclaves, this estate offers a rare fusion of luxury, privacy, and relaxed sophistication. Set on a serene, tree-lined .81-acre level lot, this 7-bedroom, 5-bathroom oasis is where inspired design meets effortless living. Stunning views of the Flatirons awaken you each morning from your bed. Those same views tease your senses from the expansive patios with fully retractable doors that blur the lines from inside to outside. Bathed in natural light from soaring windows and skylights, every detail has been thoughtfully curated. Custom walnut doors and paneling welcome you into the home and invite you to explore. The chef's kitchen is a showstopper-featuring custom cabinetry, an oversized marble island, and top-of-the-line Thermador appliances. The open-concept layout flows seamlessly into a lush backyard oasis, perfect for gatherings or quiet moments of retreat by the fire pit. The primary suite is a haven unto itself with vaulted ceilings, a spa-inspired bath, spacious walk-in closet, and private deck access. With multiple flexible living spaces-including a dedicated home office and media room, this home is ready to adapt to your every need. Located minutes from North Boulder's best hiking trails, cycling routes, farmers markets, and local eateries-yet nestled in the peaceful privacy of a mature, sought-after neighborhood. Elevated living starts here. LIVE BOULDER, LOVE BOULDER!

Full Property Details for 3633 21st St

General

  • Price: $10,000,000
  • Taxes: $29,641 (2025)
  • Status: Active
  • Type: Single Family
  • Source: IRES
  • MLS ID: 1051043
  • Updated: 2/6/2026
  • Added to Site: 14 day(s) ago

Interior

  • Interior Features: Eat-In Kitchen, Separate Dining Room, Cathedral Ceiling(s), Open Floorplan, Pantry, Wood Windows, Walk-In Closet(s), Skylights, Kitchen Island
  • Fireplace: Yes
  • Fireplace(s): Gas
  • Appliances: Gas Range, Dishwasher, Refrigerator, Washer, Dryer, Microwave, Disposal, Fire Alarm
  • Flooring: Wood

Rooms

Bathrooms

  • Total Bathrooms: 5
  • Full Bathrooms: 3
  • 3/4 Bathrooms: 1
  • Half Bathrooms: 1
  • Basement Baths: 1

Bedrooms

  • Total Bedrooms: 7

Additional Information

  • Security/Safety: Fire Sprinkler System

Exterior

  • Exterior Features: Sprinkler System, Oversized Garage
  • Porch/Patio/Deck: Patio, Deck

Parking

  • Garage: Yes
  • Attached garage: Yes
  • Garage Spaces: 3
  • Parking Features: Attached
  • Garage Description: Attached

Location

  • Area: Boulder
  • County: Boulder
  • Subdivision: 21st/Linden Sub

School Information

  • School District: Boulder Valley Dist RE2
  • Elementary School: Columbine
  • Middle School: Centennial
  • High School: Boulder

Heating & Cooling

  • Cooling Type: Wall/Window Unit(s), Ceiling Fan(s)
  • Heating Type: Hot Water, Zoned, Radiant

Utilities

  • Gas: Yes
  • Gas: XCEL
  • Sewer: Public Sewer
  • Water: City
  • Utility Description: Natural Gas Available, Electricity Available

Structural Information

  • Architectural Style: Contemporary
  • Construction: Frame
  • Exterior Const.: Frame
  • Basement: Yes
  • Basement Desc.: Full, Daylight
  • Roof: Composition
  • Windows: Skylight(s)
  • Square Feet: 6,988
  • Sq. Ft. Source: Assessor
  • Living Area: 6,988 Sq. Ft.
  • Year Built: 2024

Lot Features

  • Property View: Hills
  • Lot Size (Acres): 0.81
  • Lot Size (Sq. Ft.): 35,311
  • Fence: Yes
  • Lot Features: Wooded, Evergreen Trees, Deciduous Trees, Level, House Faces South
  • Potential Use: Single-Family
  • Zoning: RES
  • Fencing (Description): Partial, Security

Financial Considerations

  • Tax Amount: $29,641
  • Tax Year: 2025
  • Terms: Cash, Conventional

Disclosures and Reports

  • Special Conditions: Private Owner
  • Exclusions: Sellers personal property and any staging items
  • Property ID: R0004105

Listed by The Agency - Boulder (720) 577-5503

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Listing agent

— 3633 21st St —

  • The Agency - Boulder

    720-577-5503

7203941997

Get Pre-Approved Today

Be ready to buy your new home!

with our affiliated lender
NMLS#: 1598647

Get Pre-Approved

Be ready to buy your new home!

with our affiliated lender
NMLS#: 1598647

Get Pre-Approved

Schools serving 3633 21st St

School District:Boulder Valley School District Re-2
NameGradesDistance
Columbine Elementary School, Boulder, CO
3130 Repplier Street, Boulder, CO 80304
PK-50.7 mi
Centennial Middle School, Boulder, CO
2205 Norwood Avenue, Boulder, CO 80304
6-80.3 mi
Boulder High School
1604 Arapahoe Avenue, Boulder, CO 80302
9-121.9 mi
Disclaimer: School attendance boundaries provided by Pitney Bowes and are for reference only. Contact the school directly to verify enrollment eligibility.

Price & Sales History for 3633 21st St Get Price Alerts and Save Property

Date
Details
Price
Change
Source
2/06/2026
Listed
$10,000,000
122.22%
MLS
1/14/2022
Sold
$4,500,000
—
Public Record
Get Price Alerts and Save Property
Disclaimer: Historical sales information is derived from public records provided by the county offices. Information is not guaranteed and should be independently verified.

Tax History for 3633 21st St

Year
Property Taxes
Change
Tax Assessment
Change
2025
$29,641
-1%
$310,869
-9%
2024
$29,936
3%
$340,628
—
2023
$29,119
33%
$340,876
34%
2021
$21,870
-5%
$254,083
3%
2022
$22,935
5%
$246,976
-4%
2021
$21,870
-1%
$257,401
—
2019
$22,063
21%
$257,401
22%
2018
$18,273
3%
$210,766
—
2017
$17,702
7%
$210,766
10%
2016
$16,537
6%
$191,040
—
2015
$15,660
38%
$191,040
45%
2014
$11,330
2%
$131,783
—
2013
$11,080
—
$131,783
—
View All
Disclaimer: Historical tax information is derived from public records provided by the county offices. Information is not guaranteed and should be independently verified.

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*These costs are estimates, and the interest rates assume exceptional credit standing.

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NMLS#: 1598647

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Listed by The Agency - Boulder (720) 577-5503

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3633 21st St, Boulder, CO 80304 (MLS# 1051043) is a Single Family property with 7 bedrooms, 3 full bathrooms and 2 partial bathrooms. 3633 21st St is currently listed for $10,000,000 and was received on February 06, 2026. Want to learn more about 3633 21st St? Do you have questions about finding other Single Family real estate for sale in Boulder? You can browse all Boulder real estate or contact a Coldwell Banker agent to request more information.

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