Beginner
≈ 2 h 30 minSuggested range1 h 30 min – 3 h 45 min
Official LEGO® image · © LEGO Group and/or the respective rights holders. Source: LEGO Italy ↗
Architecture · SET 21023
Flatiron Building
The Flatiron's triangular outline rises through rows of windows on an urban base.
- Pieces
- 471
- Release year
- 2015
- Theme
- Architecture
- Set number
- 21023
- LEGO recommended age
- 12+
- Archived regional retail price · Germany
- 39.99 €
Archived regional retail price in the stated market and currency. It does not establish the Italian launch price; no estimated currency conversion. Brickset ↗ · Reference checked on 22 October 2026
Official English name verified at: LEGO English archive ↗ · Checked on 26 October 2026.
TIME TO BUILD
How long does it take to build Flatiron Building?
A starting point for planning your build. Times for each experience level are editorial estimates, not measurements submitted by HowLongToBuild users.
Editorial model estimate · no verified measured building time
Intermediate
≈ 1 h 45 minSuggested range1 h – 2 h 45 minExperienced
≈ 1 h 15 minSuggested range45 min – 2 hBased on one person building the set for the first time, following the original instructions and using numbered bags where supplied. Includes normal piece-finding and minor adjustments; excludes long breaks, filming, dismantling and modifications. Sources may use different methods. This range is neither a statistical interval nor a limit: your build may take less or more time.
How we estimate times · sources and method
Repeated facades and the plan's angles require order and precision. A complete first build by one person. Older sets may use unnumbered bags, so finding pieces can take longer. The broad ranges are editorial assessments, not measured averages or guaranteed limits.
Sources do not always specify the builder’s experience. The three experience bands are our editorial assessment, based on the complexity of the set and individual accounts where available.
- LEGO · official set archive ↗
Source for name, pieces, year, age, model and manuals; not a timed build.
- LEGO · set-specific manual ↗
Original set instructions considered alongside the structure when estimating the build. Not a timed community contribution.
Checked: 26 October 2026 · Method v1.0 · Limited reports; not a statistical average.
BUILT BY THE COMMUNITY
Yours could be the first building time.
0 reviewed solo building times.
No solo building times have been reviewed yet. You can still find editorial estimates under Suggested times.
Log your buildBuild your own story.
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Create a free account →BEYOND THE BRICKS
Did you know?
Inside the set
A triangular plan
The pointed end defines the building's outline.
LEGO sourceRows of windows
Vertical and horizontal repetition gives rhythm to the facades.
LEGO sourceBeyond the set
The stories, places and inventions behind your build.
A site that shaped the building
The Flatiron's outline follows the triangular plot between Broadway, Fifth Avenue and 23rd Street.
New York City Landmarks Preservation CommissionA 1902 design
The building was completed in 1902 to a design by D. H. Burnham & Co.
New York City Landmarks Preservation CommissionWritten by HowLongToBuild · Sources are linked with each story · Checked on 26 October 2026. Historical facts and story details refer to the context described.
THE COMMUNITY’S EXPERIENCE
What was it like to build?
Three separate scores from 1 to 10. For difficulty, 1 means very easy and 10 means very difficult.
No approved ratings yet. Scores are never generated by this site or inferred from the recommended age.
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Specific steps, useful checks and sticking points. Contributions appear after moderation, in their original language. Do not upload instruction pages or personal contact details.
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Sign in to contributeSET THE MOOD
A soundtrack for your build
· Selected for the subject and atmosphere
One underlying pattern supports variations with different characters, like modules changing roles within a structure. A pairing for symmetry, façades and precision mechanisms, with solo piano illuminating the details.
OUR PICK
J. S. Bach: Goldberg Variations
Víkingur Ólafsson
Variations, symmetry and counterpointEditorial suggestions, not official soundtracks for the set. External services may require an account or subscription; editions and availability can vary by country. Suggest another soundtrack →
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YOUR NEXT BUILD
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Sets from the same theme or with similar suggested building times. The ranges shown are for intermediate builders.
Official LEGO® image · © LEGO Group and/or the respective rights holders. Source: LEGO Italy ↗
Official LEGO® image · © LEGO Group and/or the respective rights holders. Source: LEGO Italy ↗
Farnsworth House
546 pieces · 12+
1 h 15 min – 3 h
Suggested time · Intermediate
Same theme, a new build
Official LEGO® image · © LEGO Group and/or the respective rights holders. Source: LEGO Italy ↗