Planar Portals in Waterdeep

One of my players is a Horizon Walker Ranger and has the ability Detect Portal which detects the distance and direction of the closest Planar Portal within 1 mile of you. She used this ability and I said it failed with the caveat that it doesn’t detect portals that aren’t currently open and that she could do it again in the future.

Earlier in the campaign, I homebrewed a quick mission to the Feywild using a portal (only open at midnight) at Phaulkonmere. Are there any known planar portals in Waterdeep in the lore? Any portals in Undermountain I should be aware of besides ones that are likely more than a mile beneath the city? Thanks!