The Colloquium will be held at Długa street which is in the Old Town District of Warsaw. The Old Town in Warsaw is charming and beautiful, with colourful buildings, churches and monuments. Cozy cafes and restaurants await, as well as lots of boutique shops. Probably the best place to stay in Warsaw for tourists. It offers luxurious hotels, more modest options as well as boutique apartments. 
Some of the accommodations we recommend:
IBIS Hotel Stare Miasto - A great budget option, centrally located just a 10- to 15-minute walk to Długa Street and Old Town, and close to a few pubs and cafes. There are multiple public transport options very close to the hotel. The onsite Ibis Kitchen restaurant serves a daily buffet breakfast (extra) and drinks can be had in the Lounge bar. The air conditioned rooms are comfortable and modern with satellite TVs and a working space. Complimentary fruit and bottled water are also available to guests.
Mamaison LaRegina Hotel - Upscale 5-star accommodation centrally located in a historic palace. A 5 minute walk to Długa Street, and just a 10-minute walk to the Royal Castle and Market Square, also 5 minutes to the Multimedia Fountain Park and bank of the Vistula. Fine dining can be found onsite at La Rotisserie, which offers indoor and outdoor seating, but lots of decent restaurants in the area. Luxury services include a spa and wellness center complete with gym, indoor swimming pool, and sauna.
Castle Inn a boutique hotel located next to the Royal Castle. It offers themed rooms designed by Warsaw artists, with most rooms offering views of the Castle or St. John’s Cathedral. Located within a 5-10 minute walk to to Długa Street. Breakfast buffet is served daily in the picturesque dining room. 

The yellow location marker indicates Długa 7 street where the Colloquium will take place.