Property

Our property consists of the following (in thousands):



	September 30, 2018		December 31, 2017
Land	$	957,362	$	1,068,022
Land held for development	57,736		69,205
Land under development	53,570		48,985
Buildings and improvements	3,045,537		3,232,074
Construction in-progress	131,309		80,573
Total	$	4,245,514	$	4,498,859

During the nine months ended September 30, 2018, we sold 17 centers and other property. Aggregate gross sales proceeds from these transactions approximated $381.7 million and generated gains of approximately $173.1 million, including properties previously classified as held for sale. Also, during the nine months ended September 30, 2018, we invested $54.7 million in new development projects.

At September 30, 2018, two centers, totaling $111.3 million before accumulated depreciation, were classified as held for sale. At December 31, 2017, three centers, totaling $78.7 million before accumulated depreciation, were classified as held for sale. None of these centers qualified to be reported in discontinued operations.