What did you do this summer vacation?

The Thames Festival London's biggest end of the summer party takes place on the 11th and 12th along the banks of the River Thames between Westminster and Tower Bridge. There are free concerts from the likes of fusion band Saravah Soul, a nighttime carnival, circuses, firework displays, markets and all manner of street performers. Free Heritage Open Days Between September 9th and 12th throughout England, historic buildings which are normally closed to the public throw open their doors to visitors. The city of London has also organized Open House London, with an additional list of open sites the following weekend (September 18-19). All in all, hundreds of wonderful buildings and tourists sights are open—for free—including the Bodleian Library in Oxford, great Masonic Temple in Covent Garden (where there is a huge painting of George Washington in full Masonic regalia), The Royal Society buildings in Westminster (where Newton and Priestley were members), and tourist attractions like the London Eye. Free The Great River Race The biggest annual race on the Thames takes place at 12:15 pm on September 25th, when river craft—everything from adapted bath tubs and Polynesian war canoes to svelte competition kayaks—gather in Ham in West London to race 21 miles to the Docklands in the East. It's far less exclusive than the more famous Oxford-vs-Cambridge boat race, but far more colorful—and if you can get hold of a boat you can even enter the race, instead of just watching it. Free The Clarence House Garden Party Between September 8th and 19th, Prince Charles throws an 11-day shindig in the gardens of his London Palace. It's to raise money for his favorite charities. Tickets are a snip at US$23—which includes privileged access to the royal lawns and flower beds, as well as a full program of entertainment. This year this includes music by Jools Holland, comedy by local stars Marcus Brigstocke and Hugh Dennis, and a fashion show by Vivienne Westwood. London Fashion Weekend A coterie of London and the world's top designers gather at Somerset House in the city center between September 23-26 to parade their latest wares on the catwalk and offer the hoi polloi the chance to buy their gowns and garb for 70% of the retail price. Designers who will be showing this year include John Galliano, Chloe, Mawi, Herve Leger, Vivienne Westwood, Beatrix Ong and Pyrus. Get tickets (from US$20) and more information here.

Jazz à la Villette (through September 12) The city's premier jazz festival takes place every fall in and around the Parc de la Villete (19th arrondissement). The 2010 lineup includes Afro-Cuban stars Chucho Valdés and Archie Shepp, proto-rap pioneer Gil Scott-Heron, and some high-energy Klezmer from David Krakauer and SoCalled. Ticket prices begin at €12 (about $15), and the full program of events can be found here. Journées Européennes du Patrimoine/Heritage Days (September 18-19) During one weekend every year, hundreds of Paris museums and monuments open up for free and host special events for the public. Crowds flock to peek behind the curtain at the presidential palace (Palais de l'Elysée) and hundreds of other monuments. The official website, which includes events in cities across France, is hard to navigate, but you'll find a program of events organized by arrondissement here. Festival America (September 23-26) This annual literary festival celebrates authors from all over the Americas and features some very special readings. Many are just outside of the city in Vincennes (near the classical music festival listed below), but you'll find one of the best around the corner from the Eiffel Tower: Richard Russo at the American Library on September 23. The full program of events is here. Portes ouvertes des ateliers de Ménilmontant (September 24-27) The east side of Paris has the city's highest concentration of working artists, and the last weekend of September promises to open the doors to their studios. This annual event provides a good excuse to ramble through the Ménilmontant neighborhood near the Père Lachaise cemetery. Stop by the organizers' office at 43 rue des Panoyaux (20th arrondissement) to pick up a map of participating studios, or visit the website for more information. The Paris Techno Parade (September 25) While techno music isn't every traveler's cup of tea, watching this annual parade is a fun way to witness what French youth culture looks like today. Traffic will be blocked for hours on this Saturday afternoon while thousands of young people dance in the streets. To catch a glimpse, line up along the parade route somewhere between its starting point at Denfert-Rochereau around noon and its final destination at Bastille at 8 p.m. Bonus: two August events that are continue through September: Festival Silhouette (August 28-September 5) This festival picks up where the Cinéma au Clair de Lune leaves off, screening free outdoor films in the Parc des Buttes Chaumont (19th arrondissement). The format for this one is short films, which are screened each night at 10 p.m. following free concerts that begin around 7:30 p.m. Festival Classique au Vert (August 7-September 26) Free classical music concerts take place every Saturday and Sunday afternoon in the beautiful Parc Floral. This flowering garden inside the Bois de Vincennes (12th arrondissement) is a great place to picnic with friends before and during the performance. Entry to the Parc Floral is €5 (about $6.50), but the concerts are free.

While the cable cars are much celebrated, the F-Line Market Street Railway is another historic transit option that shouldn't be missed. (Thanks, reader Jaime Raba for reminding us about them!) The F-Line runs from Fisherman's Wharf, along the Embarcadero, and up Market to the Castro. The brightly colored vintage streetcars were imported by the city from places around the world, from Australia to England, Philadelphia to St. Louis. On any given day, as many as 20 different trolleys are on the street. Perhaps the most notable is the 1934 open air roofless "boat tram," strung with lights that came from the seaside resort town of Blackpool, England. Kids (and kids at heart!) will especially get a kick out of riding the train and hearing the old-fashioned bell ring at each stop. History buffs should stop by the SF Railway Museum south of the Ferry Building for exhibits and more information. Check out the website for a background guide to the origin of the different trolleys. The F-Line runs every 5-20 minutes from approx. 6:00 AM until 11:20 PM. As a part of Muni, transfers work throughout. $2 for adults, $.75 for youth and seniors, and free for kids under 5. streetcar.org Museum, 77 Steuart Street, (415) 974-1948, Free, Open Tuesday–Sunday 10:00am–6:00pm

I'm leaving soon for Florence, where I'll be renting an apartment, seeking out the best bars for an aperitivo, and exploring what's new since my last visit. The sandwich shop 'ino and the Museo Nazionale Alinari della Fotografia in Piazza Santa Maria Novella are high on my list. I'm also curious to find out more about the young mayor's ambitious plans. So I've got my questions, but I'm wondering what you would like to know about Florence? Maybe it's something about Florentine etiquette, local markets and shops, how to tackle the world-famous museums, or where to find some green space in the crowded city. Now's your chance to ask, and I'll see what I can fit in. PREVIOUSLY Share your favorite hotels and restaurants in Florence