<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-03-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000914713</issuerCik>
        <issuerName>MILLS CORP</issuerName>
        <issuerTradingSymbol>MLS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001063761</rptOwnerCik>
            <rptOwnerName>SIMON PROPERTY GROUP INC /DE/</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>225 W. WASHINGTON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>INDIANAPOLIS</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>46204</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001022344</rptOwnerCik>
            <rptOwnerName>SIMON PROPERTY GROUP L P /DE/</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>225 W. WASHINGTON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>INDIANAPOLIS</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>46204</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2007-03-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>28145000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.25</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>77080908</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2007-04-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>77080908</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On March 30, 2007, SPG-FCM Acquisition, Inc. (&quot;Sub&quot;) acquired an aggregate of 77,080,908 shares of common stock, par value $0.01 per share, of The Mills Corporation (the &quot;Company&quot;) through (a) the contribution by SPG-FCM Ventures, LLC (&quot;Purchaser&quot;) of 48,935,908 shares; (b) the contribution of funds managed by Farallon Capital Management, L.L.C. (&quot;Farallon&quot;) of 6,145,000 shares, in exchange for a certain amount of shares of Sub; and (c) the acquisition by Sub of 22,000,000 shares through the exercise of its option granted pursuant to the Short Form Merger Option Agreement (the &quot;Option Agreement&quot;) dated February 12, 2007 among the Company, Purchaser and Sub, at a consideration per share equal to $25.25, payable in the form of (i) $0.01 in cash per share and (ii) a promissory note from Purchaser for $25.25 per share less $0.01 per share (or an aggregate principal amount of $555,280,000).  The amount of securities shown in this row is owned beneficially by Purchaser, through Sub.</footnote>
        <footnote id="F2">Sub is a wholly owned subsidiary of Purchaser, and Purchaser is a joint venture between an entity owned by Simon Property Group, Inc. and Simon Property Group, L.P. (collectively &quot;SPG&quot;) and Farallon.  As a result of this relationship, SPG may be deemed to share beneficial ownership of the securities shown in this row.</footnote>
        <footnote id="F3">On April 3, 2007, the acquisition of the Company by Purchaser was completed by means of a merger of Sub with and into the Company (the &quot;Merger&quot;).  In the Merger, all outstanding shares of common stock of the Company (the &quot;Shares&quot;) (other than shares held by the Company, Purchaser or any subsidiary of Purchaser, which were cancelled pursuant to the Merger, and shares as to which appraisal rights are perfected under Delaware law) were converted into the right to receive the same $25.25 in cash per share, without interest, as was paid in the tender offer by Purchaser for all outstanding shares of the Company.  As a result of the consummation of the Merger, and as a result of the relationship between Sub, Purchaser and SPG described in Footnote (2), SPG may be deemed to share beneficial ownership of all of the outstanding Shares of the Company.</footnote>
        <footnote id="F4">Under the terms of the Merger, the number of Shares outstanding immediately after the Merger is significantly less than when there were publicly traded Shares and is not related to the number of Shares prior to the Merger.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Stephen E. Sterrett Stephen E. Sterrett, Executive Vice President and Chief Financial Officer, on behalf of Simon Property Group, Inc.</signatureName>
        <signatureDate>2007-04-03</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stephen E. Sterrett Stephen E. Sterrett, Executive Vice President and Chief Financial Officer on behalf of Simon Property Group, Inc., as general partner of Simon Property Group, L.P.</signatureName>
        <signatureDate>2007-04-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
