The Cardiff Bay Barrage will be closed to cyclists and walkers next week for a series of concerts.
Biffy Clyro, Nile Rodgers, Chic and Eric Prydz are among those set to play at Alexandra Head during the four-day Titan festival.
It means the key route linking the Bay with Penarth will be shut to pedestrians at these times:
Cardiff Council say the closure was needed to prevent crowds from blocking access to walkers - but the move has been attacked by opposition parties.
Joe Carter, Liberal Democrat councillor for Pentwyn, told the Local Democracy Reporting Service: ''It’s really surprising to see a major walking and cycle route closed over the weekend to allow a concert to take place. The weekend is the busiest time for the barrage, particularly for the last weekend of the Aqua Park.''
''It is hard to imagine a major road being closed, and yet the needs of pedestrians and cyclists are ignored. The barrage and access road should be wide enough to allow everyone to use it. We hope the council can reconsider and find a way of keeping it open to everyone.''
The barrage will be closed from the Porth Teigr roundabout to the Penarth end of the barrage. Only people going to the concerts will be able to enter and exit the events at Porth Teigr.
Around 11,000 people are expected to attend the events at Alexandra Head since the beginning of the COVID pandemic.
The council says the closure will reduce the risk of similar scenes at the Euro 2020 final at Wembley, when crowds stormed the entrance and forced their way in.
Councillor Peter Bradbury, cabinet member for culture, leisure and sport, said the barrage would stay open to everyone until 4.30pm on Thursday and until midday over the weekend.
He added: ''If you’re travelling from Penarth, please make sure you’re on the Cardiff side of the barrage before the site closes. All access to the gigs will be on the Cardiff side of the barrage where security, soft ticket checks and Covid checks will be set up by the event organisers.''
''Up to 11,000 ticket holders will be at these events each day so it would be difficult, if not impossible, for commuters or cyclists to cross the barrage safely.''
''Such high-profile acts attract a lot of interest and if the barrage remained open, potentially large crowds could gather.''
''Closing the site will reduce the risks associated with the gathering of large crowds in the area, including blocked access for people commuting or walking, preventing emergency vehicles accessing the area if required, risk of overcrowding and congestion on entry and exit to the events and the potential for non-ticket holders to get into the event, which could lead to a similar situation seen at the recent European Championships at Wembley.''
''This is the first time events have been held at Alexandra Head since before the pandemic and we want everyone to have a safe and enjoyable return to outdoor events at this venue.''
But Councillor Mike Phillips, Conservative councillor for Whitchurch & Tongwynlais, argued active travel cannot be compromised for a concert.
He told the LDRS: ''Disenfranchising walkers and cyclists suggests we are not serious about embedding healthier forms of transport into our systems.''
Closure signs will be in place around the area next week - for more details, visit the Harbour Authority website.