SEC Form 3 
FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940 	  
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1. Name and Address of Reporting Person*
THOMPSON SAMME L	

(Last)	(First)	(Middle)	
116 HUNTINGTON AVENUE	

(Street) 
BOSTON	MA	02116	

(City)	(State)	(Zip)	
	2. Date of Event Requiring Statement (Month/Day/Year)
08/08/2005 	3. Issuer Name and Ticker or Trading Symbol 
AMERICAN TOWER CORP /MA/ [ AMT ] 		
		4. Relationship of Reporting Person(s) to Issuer 
(Check all applicable) 
X	Director		10% Owner	
	Officer (give title below)		Other (specify below)	
	
	5. If Amendment, Date of Original Filed (Month/Day/Year)				
			6. Individual or Joint/Group Filing (Check Applicable Line) 
X	Form filed by One Reporting Person	
	Form filed by More than One Reporting Person	
	
Table I - Non-Derivative Securities Beneficially Owned	
1. Title of Security (Instr. 4) 	2. Amount of Securities Beneficially Owned (Instr. 4) 	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 	4. Nature of Indirect Beneficial Ownership (Instr. 5) 	
Class A Common Stock(1) 	8,258	D		
Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities) 	
1. Title of Derivative Security (Instr. 4) 	2. Date Exercisable and Expiration Date (Month/Day/Year)	3. Title and Amount of Securities Underlying Derivative Security (Instr. 4) 	4. Conversion or Exercise Price of Derivative Security 	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 	6. Nature of Indirect Beneficial Ownership (Instr. 5) 	
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares				
Explanation of Responses:	
1. Pursuant to the Agreement and Plan of Merger, dated May 3, 2005, by and among American Tower Corporation (the "Company"), Asteroid Merger Sub, LLC, and SpectraSite, Inc. ("SpectraSite"), each outstanding share of SpectraSite common stock was automatically converted into 3.575 shares of the Company's Class A Common Stock.	
Remarks:	
	
	/s/ Samme L. Thompson	08/10/2005	
	** Signature of Reporting Person	Date	
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.	
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).	
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).	
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.	
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.	
LIMITED POWER OF ATTORNEY
FOR SECTION 16 REPORTING OBLIGATIONS

Know all by these presents, that the undersigned hereby
makes, constitutes and appoints each of William H. Hess,
Bradley E. Singer and Nathaniel B. Sisitsky, signing singly
and each acting individually, as the undersigned's true and
lawful attorney-in-fact with full power and authority as
hereinafter described to:

(1)  execute for and on behalf of the undersigned, in the
undersigned's capacity as a director of American Tower
Corporation (the "Company"), Form ID, Forms 3, 4, and 5
(including any amendments thereto) in accordance with
Section 16(a) of the Securities Exchange Act of 1934 and
the rules thereunder (the "Exchange Act");

(2)  do and perform any and all acts for and on behalf
of the undersigned which may be necessary or desirable to
prepare, complete and execute any such Form ID, Form 3, 4,
or 5, prepare, complete and execute any amendment or
amendments thereto, and timely deliver and file such form
with the United States Securities and Exchange Commission
and any stock exchange or similar authority;

(3)  seek or obtain, as the undersigned's representative
and on the undersigned's behalf, information regarding
transactions in the Company's securities from any third
party, including brokers, employee benefit plan administrators
and trustees, and the undersigned hereby authorizes any
such person to release any such information to such
attorney-in-fact and approves and ratifies any such release
of information; and

(4)  take any other action of any type whatsoever in
connection with the foregoing which, in the opinion of such
attorney-in-fact, may be of benefit to, in the best interest of,
or legally required by, the undersigned, it being understood
that the documents executed by such attorney-in-fact on behalf
of the undersigned pursuant to this Power of Attorney shall be
in such form and shall contain such terms and conditions
as such attorney-in-fact may approve in such attorney-in-fact's
discretion.

The undersigned hereby grants to each such attorney-in-fact
full power and authority to do and perform any and every act
and thing whatsoever requisite, necessary, or proper to be done
in the exercise of any of the rights and powers herein granted,
as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution
or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or substitutes,
shall lawfully do or cause to be done by virtue of this power
of attorney and the rights and powers herein granted.
The undersigned acknowledges that the foregoing attorneys-in-fact,
in serving in such capacity at the request of the undersigned,
are not assuming nor relieving, nor is the Company assuming
nor relieving, any of the undersigned's responsibilities to comply
with Section 16 of the Exchange Act.

The undersigned acknowledges that neither the Company
nor the foregoing attorneys-in-fact assume (i) any liability
for the undersigned's responsibility to comply with the requirement
of the Exchange Act, (ii) any liability of the undersigned for any
failure to comply with such requirements, or (iii) any obligation
or liability of the undersigned for profit disgorgement under
Section 16(b) of the Exchange Act.

This Power of Attorney shall remain in full force and effect
until the undersigned is no longer required to file Forms 3,
4, and 5 with respect to the undersigned's holdings of and
transactions in securities issued by the Company, unless earlier
revoked by the undersigned in a signed writing delivered
to the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this
Power of Attorney to be executed as of this 10th day of August, 2005.

/s/  Samme L. Thompson

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