Roskilde is in Zealand, Denmark. Roskilde is an ancient city dating from the Viking age.
From Copenhagen Central Station (København H) it is about a 25 minute trip. Nearly all trains leaving Copenhagen besides those leaving for Elsinore or Sweden stops in Roskilde, but you would normally have to pay an extra fee if you jump on a Intercity train (i.e. trains to Jutland). Regional trains bound for Odense, Kalundborg or Nykøbing Falster are your best choices (they are marked with a green "Re" sign on platform screens). There is also a small branch line with occasional trains to Køge.
Intercity buses to and from Jutland lines 882 to Fjerritslev and 888 to Århus/Aalborg, makes stop at the Q8 gas station at Darupvej 2, by the highway. It is quite far from the city center, but there are several bus lines connecting from Roskilde Station, e.g. 600S
Important regional buses includes 600S which runs an arch around Copenhagen proper from Hillerød in the north (Frederiksborg castle) to Hundige Station in the south. 233 runs between Roskilde and Lejre Forsøgscenter, 234 connects with Slagelse and finaly 229E and 239 with Frederikssund.
Roskilde Airport (IATA: RKE, ICAO: EKRK)  is Denmark's premier General Aviation facility with planes taking off or landing, every 5 minutes througout the day. It is also the main base for un- or semi scheduled taxi flights to the Kingdoms more remote islands; Copenhagen Airtaxi  offers flights to Samsø, Læsø and Anholt for between 1,000-1,500 Kr, and more or less works as a regular airline, with flights bookable on the company website. Other options include: Samair to Samsø and Starling to Ærø.
You can easily walk from the train station to the main square with the cathredral and from there to the Viking Ship museum.
Map of Central Roskilde
Roskilde Cathedral (Roskilde Domkirke), . On UNESCO's World Heritage List. This is where Danish kings and queens have been buried for a thousand years. Home to the Cathedral Museum.25 Kr.
Roskilde Former City Hall, Stændertorvet 1.
Roskilde Palace, Stændertorvet 3. Home to two exhibitions, the Museum of Contemporary Art  and the Palace Wing .
Roskilde Station, Jernbanegade 1. The oldest existing train station in Denmark.
Historic granite tiles, Skomagergade.
The Giant Jars, Hestetorvet.
Parks and nature
Ledreborg Palace & Park, Ledreborg Alle 2, Lejre, .
The Viking Ship Museum, Vindeboder 12 (Follow the signs from the cathredral), ☎ ''+45'' 46300200 (email@example.com), . 10AM-5PM. A museum with several original viking ships, a viking research center, a harbour with copies of viking ships, a shipyard making new ships.95 Kr, students 75 Kr, children free.
Roskilde Museum, Sankt Ols Gade 18, ☎ +45 46 31 65 29, . Local history museum, but well in tune with other attractions, it also has a good collection of Viking archaeological finds, some connecting to the saga's about the legendary Beowulf.25 Kr.
The legendary Roskilde festival  is still going strong despite 40 years of sex, drugs and rock'n'roll! started by a group of friends in 1971 inspired by the Woodstock festival, it has grown from a few thousand guests in its first year, to over 115.000 visitors from all over the world, and is routinely sold out with over half the tickets sold outside of Denmark.
The festival takes place in late June early July on Roskilde Dyreskueplads south of the city. To Get in there are several options; from Monday-Sunday during the festival trains depart from Roskilde Station to the festivals very own station inside the camping area (West) every 30 minutes for 20 kroner. There are also shuttle buses from Roskilde Station to the camping area (East) all day during the festival. When arriving at the festival you exchange your ticket to an armband/bracelet which gives you access to both the camping area, and the stage area.
Many people show up a week before the music starts to get their tents up so they can sleep close to the stage area, and limit walking as much as possible as the camping area is huge! A good tip is securing a place as far from trees and fences as possible, since they in essence become one big urinal during the festival, if rain is forecast, you should also attempt to camp as far from the marked walkways, preferably on a slope, since mud quickly becomes and issue.
On the camping grounds there are several service areas with food stalls and supermarkets to stock up with eat & drink, some also have first aid, toilets and showers. Inside the stage area there are also many many restaurants and bars - most of them with a theme, and some of them are really huge and elaborate. There are also many shops where you can buy necessities and other rubbish.
Music is playing from Thursday - Sunday and are usually varied, with some international headline acts, and much experimental and indie music and the smaller stages.
Sail in a viking boat on the fjord, (at the viking centre).
Sagnlandet Lejre, Slangealleen 2, 4320 Lejre (Bus 233 from Roskilde station), ☎ +45 4648 0878 (firstname.lastname@example.org), . Become a Viking for a day, in this spectacular hands on history museum.
Capella Play, Ro's Torv 51A.
Roskilde Golf Klub.
The Path of the Gods (Gudernes Stræde), . 64km path.
On Roskilde festival the nearest supermarket is Fakta at Køgevej 108, about 1300 meters (a 15-20 minute walk) due north (past the highway) from the eastern entrance. The downtown area which has a pedestrianized area full of different shops is a further 1½ km away (or 30-40 minutes by foot).
RO's Torv, Københavnsvej 29 (a few hundred meters east of the station beyond the tracks), ☎ +45 4638 0680, . M-F 10AM-7PM, Sa 10AM-4PM. A fairly attractive mall with 90 different stores and a cinema.
Algade/Skomagergade. Pedestrian street and main shopping street in town.
Jensens Bøfhus, Skomagergade 38, ☎ +45 4632 2510, . M-Th 11AM-10PM, F-Sa 11AM-11PM, Su noon-10PM. Mains 100-200 Kr, menus from around 150 Kr.
Restaurant Shanghai, Skomagergade 4, ☎ +45 4635 0182 (fax: +45 4632 0831), . Five course menu 108 Kr, main courses from around 70 Kr.
Snekken, Vindeboder 16, ☎ +45 4635 9816, . 11:30AM-11PM; kitchen 11:30AM-4:30PM, 6PM-9PM. Restaurant at Viking Ship museum with a view over Roskilde Inlet.Mains around 200 Kr.
MS Sagafjord, at the harbour next to the Viking museum, ☎ +45 4675 6460 (email@example.com), . Old Restaurant ship. You can have lunch, tea or dinner on Roskilde Fjord.95 Kr plus e.g. 365 Kr for a three course evening menu.
Restaurant Mumm, Karen Olsdatters Stræde 9, ☎ +45 4637 2201, . Three course menu 425 Kr.
Mary's, Støden 9, ☎ +45 4632 4600. Combined club and sports café.
DANHOSTEL Roskilde Vandrerhjem, (next to the Viking museum), ☎ ''+45'' 46352184, . Hostel at the harbour next to the Viking museum. Have dormitories and family rooms150 Kr.
Soviro Bed&Breakfast, Skovbovængets Allé 17, ☎ +45 2077 4482 (firstname.lastname@example.org), . Listed rates for doubles from 450 Kr.
Mr. Janny Motel, Motelvej 28, ☎ +45 4635 4385.
Bed&Breakfast Roskilde, Langagervej 19A, ☎ +45 4636 3702, 2446 9623 (email@example.com), . Doubles from 450 Kr, apartment 1,000 Kr.
Hotel Comwell Roskilde, Vestre Kirkevej 12, Himmelev, ☎ +45 4632 3131 (firstname.lastname@example.org, fax: +45 4635 0835), . Rooms with free internet, some with view of Roskilde Inlet.Listed rates for doubles from 1,445 Kr.