But memories of the vicious year-long war in the city die hard. In the ruins of east Mostar, the main feature film has frequently been preceded by footage of the systematic destruction last year of the 16th- century Turkish bridge across the turquoise river. On the west bank, the Croatian soldiers who shelled the bridge, nominal allies of those across the river, are still expelling Muslim residents to the east.
The Muslim-Croatian war is over, the politicians say, and the Geneva peace plan, focus of frantic efforts by Russian and Western diplomats this week, assumes only two warring factions: the Bosnian Serbs and the new federation. But although the shelling has stopped in Mostar and central Bosnia, reconciliation is a far off and the alliance against the Serbs is shaky.
Hopes for the reunification of Mostar, and for the realisation of the federation, now rest on the shoulders of a German ex-mayor, who yesterday took over the administration of the city in the name of the European Union. It will be the big test for the tentative Bosnian federation, said Hans Koschnick, a former mayor of Bremen who is not entirely optimistic about his task.
'I have always told people the chances of success . . . lie a shade over 50 per cent, meaning that the chances of failure are just under 50 per cent,' he said recently. 'That is a damn high risk.'
Mr Koschnick insisted on the demilitarisation of Mostar before he assumed his position, but it seems that most soldiers swapped one uniform for another. 'I believe the police force has grown in size - on both sides - almost to match the (number of) troops before the agreement,' said Jerrie Hulme, United Nations High Commissioner for Refugees (UNHCR) chief in Mostar.
The EU is dispatching 200 police officers to assist the administrator, but made it clear they are not there to impose order by force. 'If a shot is fired, I will have to send the international force straight home,' Mr Koschnick said.
The debris of war has been cleared away, most of the sniper screens have been dismantled and police from both sides man a checkpoint on the truce line by a rickety bridge across the river; but many obstacles to a workable peace remain. In Mostar, these are mostly to be found on the west bank, a sinister, lawless place where the streets are filled with aggressive young men in uniform, three of whom ordered a Muslim family to leave their home 10 days ago, according to the UNHCR. 'There is no place for balija in Mostar,' they said, using a derogatory term for Muslims.
For their part, the Bosnian authorities on the east bank have refused to let civilians leave; as a result, thousands are still crammed into the cellars of buildings shelled to rubble. And the UN reports that 3,500 Croats have been expelled from the Muslim-held town of Zenica since the peace deal was signed in March.
UN officials and other aid workers are divided over the degree of official complicity in the 'ethnic cleansing' of Mostar, but all agree that law and order is notably absent from the west. 'I think that we're down to the post-war problems of warlords and black marketeers,' said Mr Hulme. But a colleague, who asked not to be identified, disagrees. 'I believe these gangs are operating under the protection of some official body,' he said. 'When everyone in the city knows their names . . . and they still own the cafes, and sit in them drinking, something is wrong with the justice system.'
The aid worker blames politicians in the self-styled 'Croat Republic of Herzeg-Bosna', the statelet in western Herzegovina, who are 'very much opposed to the federation'. They have argued that Mostar should remain split into two municipalities by the river running through it, and their position is likely to harden. 'The real price for the Croats, the price tag for the federation, is giving up power in Mostar and the idea that it can be the capital of some Croatian mini-state,' said the aid worker. 'That hasn't happened yet.'
It is clear that Herzeg-Bosna still looks to Zagreb rather than Sarajevo. Shops in west Mostar accept the kuna, Croatia's currency, and the deutschmarks favoured elsewhere in Bosnia. Anto Valentic, a senior Bosnian Croat official, recently told reporters that the Bosnian side 'must be orientated towards Western culture and civilisation' - a remark unlikely to endear him to the Muslim sophisticates of Sarajevo and east Mostar. He added: 'We can't really talk about (federation) as irreversible.'
In theory, the Bosnian federation is to seek confederation with Croatia, an idea that remains deeply unpopular in Zagreb. Washington cajoled the Croats and Muslims into a deal when it became clear their war was suicidal: it was driven by fear of the Serbs rather than a desire for unity. And the Serbian troops entrenched nearby might yet help cement the deal.
'There is still the overlying threat from the hill to the east,' said Mr Hulme. 'Nobody knows what the Serbs are going to do. That might work in favour of a joint Mostar.'