Gampaha Asgiriya Raja Maha Viharaya is an ancient cave temple lying on top of a hillock on the Gampaha Minuwangoda Road. According to legends the history of the temple goes back as far as King Walagamba ( 89-77 BC) who is said to have used the caves to hide during his exile after 104 BC. The king is said to have built hundreds of cave temples all over the country at each place where he used to hide during the recruitment of a new army to defeat the invaders.

The main ancient temple lies at the top of the Asgiriya hill.  This has been used as a forest hermitage in the ancient times.  At a later date, this temple received patronage from a regional king called Sakala Wallabha during the time of  Parakramabahu the 6th of Kotte Kingdom in the 16th century.  The cave with drip ledges has been converted into an image house which is covered with paintings belonging to the Kandyan Era. There is a bolder near the Bodhi Tree with inscriptions which has been protected by the Department of Archeology. This bolder also has a carving of the head of a horse. A carving of a Sri Pathula (footprint of Buddha) can be seen on one of the rocks. An ancient pond now abandoned lies at the top. None of which has been dated. It is believed that the name Asgiri was coined due to a horse of Prince Uttiya, the brother of King Kelanitissa being mysteriously lost on these hills.

About 100 years ago the priests had built an Alms Hall at the bottom of the hill since the benefactors offering alms were finding it difficult to climb to the top of the hill every day. Later a Buddha Image Hall and a Stupa were also built near this hall. A Bo Tree has also been planted here creating another complete temple at the bottom of the hill.

The temple is also known for a secret tunnel on the hill. This tunnel can be reached by stepping to the upper temple and turning right halfway. The access is through the jungle with thorny bushes. This path will lead you to a wide rock cave with a drip ledge. The cave becomes narrower as you walk into the cave. At the end of the cave lies the entrance to the tunnel. To reach the tunnel you would need to crawl between the rock and the floor. The cave entrance is now carved in cannot be accessed.

It is believed that there is a vast treasure hidden inside the tunnel and some believe that this tunnel was a secret route to pilikuththuwa rajamaha viharaya which lies about 8 km away.

There is also a deep hole on the rock next to the Stupa at the top. People believe that a treasure had been hidden inside this rock and covered with another stone and treasure hunters have destroyed the cover and plundered the valuables. Today only a hole covered by sandbags remains.