House Hightower of the Hightower is one of the most important and powerful vassals of House Tyrell (and before them of House Gardener). Their seat is the Hightower in the city of Oldtown within the Reach. The sigil of House Hightower is a stone white watchtower, with a fire on the top. Their words are "We Light the Way". They possess a Valyrian steel sword called Vigilance. Members of the house are considered loyal and stalwart. The Hightowers can be legitimately referred to as being either "of Hightower" or "of Oldtown."
House Hightower holds the lord paramouncy of the Reach at the new capital of Oldtown.
The Hightower is a castle and lighthouse in the port of Oldtown atop Battle Island. It is the seat of House Hightower, one of the most powerful families of the Reach.
According to a semi-canon source, the Hightower stands in the center of Oldtown, the city having grown around it. It is a massive stepped tower with a beacon on top to guide ships into port. It is one of the tallest structures in the Seven Kingdoms. It is speculated by fans that it is one of the nine Wonders Made by Man written about by Lomas Longstrider.
Oldtown is one of the largest cities in Westeros and is by far the oldest, built by the First Men before the Andal invasion. The city is located in the south-west of the Reach, at the mouth of the river Honeywine where it opens onto Whispering Sound and the Sunset Sea beyond. It is the western terminus of the Roseroad from Highgarden and King's Landing. House Hightower have their seat at the Hightower in Oldtown. The city also hosts the Citadel.
Prior to the First Era
The family is very old, existing since the dawn of days when they were petty-kings. During the coming of the Andals and the creation of the Kingdom of the Reach by House Gardener, the Hightowers allied with the newcomers. Thus they were able the keep their wealth, lands and privileges. The Hightowers were integral in the foundation of the Citadel.
Lord Gylen Hightower schemed against his liege lord Baelor Tyrell of House Tyrell . He kidnapped his daughter, which kicked off the events of the Ascent of the Lion. Lord Gylen along used the Golden Company and troops from House Manderly to sack Highgarden and burn it to the ground while the Tyrells were marching with King Harys Baratheon to take back his throne.
Lord Gylen was given the Lord Paramoucy of the Reach and moved its seat to Oldtown.