The four cities hoping to stage the 2016 Olympic Games have made their all-important pitches to the International Olympic Committee (IOC).
Leaders from Madrid, Tokyo, Chicago and Rio de Janeiro were in the Swiss city of Lausanne to address 93 of the 107 IOC members who will vote in October.
IOC President Jacques Rogge insisted all the cities were capable of staging a "superb Games".
He added: "It is going to be a difficult choice for my colleagues."
Officials from Chicago, who want to hold much of the Games in the city centre, were upbeat after their pitch despite a protest held by a group of Chicagoans opposed to the bid.
Bid cities had 45 minutes to make their case, followed by a 45-minute question and answer session. IOC members are permitted to visit the bid teams in their hotel suites afterwards.
The cities were asked to focus on the technical details of their bids.
Speaking on the eve of the presentations, IOC president Jacques Rogge said that although members would be looking for financial assurances, the commercial strength of the candidates should not be the key issue for selecting the host city.
"Economics should not drive our decision," Mr Rogge said at the end of a two-day IOC executive board meeting.
"Frequently in the past we did not necessarily go for the richest city and I believe we were right to do that.
"Ultimately it is not the economics but leaving a sustainable legacy. When we leave, we want it to be a bonus for the city, the region and the country."
The race to host the 2016 Olympics has been described as one of the closest in history.
Chicago, with President Barack Obama's support, is perhaps a slight favourite, says BBC World Service Sports reporter Alex Capstick.
Wednesday's presentations are unlikely to make or break a candidate, our correspondent said, but at such a late stage of the bidding process they will be desperate to deliver a flawless performance.
IOC delegates have been barred from visiting candidate cities since the Salt Lake City bribes-for-votes scandal in 1999, so this week's programme was arranged to give the bid teams direct contact with the members.