1 Kings 3:2, 4

But [in the meantime] the people were still sacrificing [to God] on the high places (hilltops) [as the pagans did to their idols], for there was no [permanent] house yet built for the Name of the LORD.

The king went to Gibeon [near Jerusalem, where the tabernacle and the bronze altar stood] to sacrifice there, for that was the great high place. Solomon offered a thousand burnt offerings on that altar.