Property

Our property consists of the following (in thousands):



	September 30, 2017		December 31, 2016
Land	$	1,094,096	$	1,107,072
Land held for development	70,715		82,953
Land under development	48,805		51,761
Buildings and improvements	3,374,867		3,489,685
Construction in-progress	78,798		57,674
Total	$	4,667,281	$	4,789,145

During the nine months ended September 30, 2017, we sold 12 centers and other property. Aggregate gross sales proceeds from these transactions approximated $223.2 million and generated gains of approximately $86.6 million. Also, during the nine months ended September 30, 2017, we invested $44.9 million in new development projects, which includes the purchase of the retail portion of a mixed-use project in Seattle, Washington that was subject to a contractual obligation at December 31, 2016.

At September 30, 2017, two centers, totaling $16.6 million before accumulated depreciation, were classified as held for sale. At December 31, 2016, one center, totaling $1.6 million before accumulated depreciation, was classified as held for sale. None of these centers qualified to be reported in discontinued operations, and each has been sold subsequent to the end of the applicable reporting period.