We stayed at the Castello Seeschloss in mid June 2006. We were initially a little disappointed in the hotel and the town of Ascona. Ascona has a very busy, touristy pedestrian promenade along the lake, however, the views of the lake and surrounding hills from the promenade are lovely. The hotel is directly on the promenade with lots of pedestrian traffic. We were glad not to be staying in the most expensive "castle room" since it directly overlooked the promenade and one night a community talent show (teen models) was held directly in front of the castle tower with booming music and loudspeakers until midnight.
The interior public rooms of the hotel are beautiful with stunning stonework and tile floors, wrought iron etc.
Most of the rooms face an interior garden courtyard with beautiful tropical plantings and a small outdoor swimming pool. Many rooms also have small patios with a small table and two chairs.
Our room was also a disappointment initially since the furnishings were tired and in need of a replacement about a decade ago. In the US a room of this quality would go for much much less. The garden area outside of our room was so lovely and peaceful that after a day we got over our disappointment with the room.
I had phoned ahead to be sure our room would be airconditioned and was told that the expensive castle rooms had airconditioning that was "turned off at midnight" so we requested a quiet garden room and were assured the a/c functioned 24 hrs per day. Our a/c consisted of a motel type unit that was ineffective. The only time you could feel any cool air was if you positioned a chair inches from the a/c. Our friends had a room with a better a/c unit and their room was relatively cool but not up to US standards.
The heat and humidity level in Ascona were almost unbearable. The only relief we got was going up to higher elevations e.g. the Centovalle and another mtn valley. A boat ride was also very pleasant with good breezes and wonderful views.
Air conditioning is almost non existent in Switzerland- even restaurants, grocery stores and museums lack a/c. If you sat on a public bench in the shade directly in front of the lake you could catch some nice breezes. Thankfully at night it always cooled off and we slept with our windows and patio doors wide open (no screens but bugs were not a problem).
Mattress was typical Swiss extra firm (no box spring) but not uncomfortable and the linens were of high quality. The bathroom was nice and up to date. Maid service was excellent with nightly turn down service.
The front desk staff were exceptionally nice and accommodating.
The food at the restaurant was outstanding- both for breakfast and dinner. I recommend the half board plan. They also have an attractive lakeside cafe across the street/promenade with excellent food or lighter snacks.
Breakfast was extensive with a wonderful assortment of breads, fruit, cheese, soft boiled eggs etc etc. It was held in a covered patio area overlooking the gardens.
Most of the other guests were German and Swiss and appeared affluent- we encountered very few Americans in the Ticino.
Ascona overall was casual with very casual, summer dress (shorts, tank tops) acceptable everywhere although guests at our hotel dressed up a little for dinner (nice casual).
I would consider another visit to Ascona but only in the winter, spring or fall. I would also probably splurge on a higher quality hotel like the Eden Roc. If traveling in the summer again I might consider a less expensive, out of the way hotel up in the hills e.g. village of Intragna.

We stayed 3 nights here while on a month long trip thoroughout northern Italy and the Swiss Alp areas. It is a beautiful, arty, seaside town. The hotel is very romantic in its style and we elected to have our dinner there for our last night and it was fantastic. You can also take the ferry or bus to the neighboring towns of Locarno (take the tram to the top of the mountain) and to Bellizona (the castle town).

At least regarding the building, this is the most beautiful hotel in ascona. We had a wonderful room (Number 401, see posted photos: room is on the very top of the tower with fantastic lake view). Room is accessible only via spiral staircase, which is quiet exhausting yet very romantic.

Other rooms (in the tower) are with frescos but a bit more expensive than ours. Check homepage (-------) for special arrangements in low season. Room 401 costs CHF 425/night, not taken account for the 4-for-3 arrangement we had. Other, cheaper rooms (from CHF 250), also available.

Staff is very friendly, they seem to like to work in that familial atmosphre. So our stay was completely relaxing.

Another recommendation: Visit Bar Cortile, which newly openend in March 2005 - our favourite place for a drink at night before climbing the stairs to our room. It is a bit hard to find the Bar in a courtyard in midtown Ascona but worth searching.

Simply the best!!!