Property

Our property consists of the following (in thousands):



	March 31, 2018		December 31, 2017
Land	$	991,321	$	1,068,022
Land held for development	66,949		69,205
Land under development	49,000		48,985
Buildings and improvements	3,151,367		3,232,074
Construction in-progress	107,033		80,573
Total	$	4,365,670	$	4,498,859

During the three months ended March 31, 2018, we sold six centers and other property. Aggregate gross sales proceeds from these transactions approximated $260.7 million and generated gains of approximately $109.0 million. Also, during the three months ended March 31, 2018, we invested $22.6 million in new development projects.

At March 31, 2018, no property was 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.