Item 2. Properties

Offices

Our principal corporate headquarters is owned and located in Houston, Texas. In addition, we have offices throughout the U.S. in locations convenient for the management and operation of our wireless infrastructure with significant consideration being given to the amount of our wireless infrastructure located in a particular area.

Wireless Infrastructure

We own, lease or manage approximately 40,000 towers geographically dispersed throughout the U.S. Towers are vertical metal structures generally ranging in height from 50 to 300 feet. In addition, our customers' wireless equipment may also be placed on building rooftops and other structures. Our towers are located on tracts of land that support the towers, equipment shelters, and where applicable, guy-wires to stabilize the structure.

Additionally, we own or lease approximately 26,500 route miles of fiber (after giving effect to the FiberNet Acquisition) primarily supporting our small cell networks designed to facilitate wireless connectivity. The majority of our fiber assets are located in major metropolitan areas. Our small cells are typically located outdoors and are often attached to public right-of-way infrastructure, including utility poles or street lights.

See "Item 1. Business—Overview" for information regarding our wireless infrastructure portfolio including our land interests and for a discussion of the location of our towers, including the percentage of our towers in the top 50 and 100 BTAs. See "Item 7. MD&A—Liquidity and Capital Resources—Contractual Cash Obligations" for a tabular presentation of the remaining terms to final expiration of the leases for the land interests which we do not own and on which our towers are located as of December 31, 2016.

Approximately 53% of our towers are leased or subleased or operated and managed under master leases, subleases, or other agreements with AT&T, Sprint, and T-Mobile. We have the option to purchase these towers at the end of their respective lease terms. We have no obligation to exercise such purchase options. See note 1 to our consolidated financial statements and "Item 1A. Risk Factors" for a further discussion.

Substantially all of our wireless infrastructure can accommodate additional tenancy, either as currently constructed or with appropriate modifications. Additionally, if so inclined as a result of a customer request for a tenant addition, we could generally replace an existing tower with another tower in its place providing additional capacity, subject to certain restrictions.

As of December 31, 2016, the average number of tenants (defined as a unique license or any related amendments thereto for count purposes) per tower is approximately 2.2 on our towers. The following chart sets forth the number of existing tenants per tower as of December 31, 2016 (see "Item 7. MD&A—Accounting and Reporting Matters—Critical Accounting Policies and Estimates" for a discussion of our impairment evaluation and our towers with no tenants).