Two men have been arrested after putting up banners on Blackpool Tower to protest against a method of gas extraction, police said.
Lancashire Police were called to the tower at 7.25am on Saturday following reports two men had erected banners hundreds of feet up the south side.
It is understood the men gained access to the tower by dressing as builders.
They were protesting against the use of "fracking" and came down after about one hour.
A 24-year-old from East Sussex and a 63-year-old from Surrey were arrested and are being held on suspicion of criminal damage and being on an enclosed premises, police said.
Police believe the men taking part in the protest represented a website that campaigns against the use of fracking - a controversial extraction process which blasts water into rock to release gas.
Energy company Cuadrilla suspended fracking operations near Blackpool in June, over fears of a link to two minor earthquakes in the area.