Property

Our property consists of the following (in thousands):



	December 31,
	2018		2017
Land	$	919,237	$	1,068,022
Land held for development	45,673		69,205
Land under development	55,793		48,985
Buildings and improvements	2,927,954		3,232,074
Construction in-progress	156,411		80,573
Total	$	4,105,068	$	4,498,859

During the year ended December 31, 2018, we sold 22 centers and other property. Aggregate gross sales proceeds from these transactions approximated $557.3 million and generated gains of approximately $162.4 million. Also, for the year ended December 31, 2018, we invested $74.1 million in new development projects.

At December 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, and gains of $45.5 million were generated from these centers during the year ended December 31, 2018.